Blood Sugar
So I did a little searching online for "diabetes diets" and I'm quite appalled. I had no idea there was such a dearth of good information.
Cleveland Clinic is typically a good source and they have some information (above are two links from their site) but I'm frankly disappointed. I looked at Diabetes.org and they hit me up for money and apparently SELL nutritional guides or something to carry with you, but I was shocked at not being able to readily click into anything online telling me what to eat or not eat if I have diabetes.
After digging through multiple layers of links, I gave up on trying to determine if they have any useful information online. Diabetes is so strongly impacted by diet, you would think there would be a "hey, stupid!" glaringly obvious button for what people NEED to know.
I did a college level paper on Functional Hypoglycemia at age seventeen in an AP high school class. My condition predisposes me to blood sugar issues. My blood sugar issues aren't as bad as they used to be but I've spent decades managing my blood sugar with diet, not medication.
Below is stuff I historically ate before my blood sugar issues improved sufficiently for me to cavalierly drink sweet tea and other indulgences without passing out. Though I still mostly drink Diet Coke to this day, my diet doesn't have to be insanely strict anymore. It was extremely strict for some years.
Safe Drinks
Water
Unsweetened tea. (Add lemon if you must)
Unsweetened coffee
Diet Coke
Unsweetened herbal teas can add a variety of flavors safely
Other Drinks
You may be able to tolerate milk and light fruit juices with no added sugars, like Juicy Juice brand drinks. Avoid fruit juices with high fructose corn syrup as if your life depends upon it, because it does. Liquid sugar is the absolute worst stuff if you are trying to control blood sugar.
Unsweetened tea cut with a little lemonade may work if your problems aren't too extreme. Also "occasionally" and "in moderation" likely applies.
Whole Grains
Pasta is often fine even though you would think it's not because it seems to be just white flour, yet they actually seem to use special flours for pasta. As long as other foods paired with it are fine, this was never an issue for me personally. Watch what sauces etc. you top it with.
Get the brown rice, not the white rice, at Asian eateries or for cooking at home. I used to buy instant brown rice and was fine with that but white rice was hugely problematic. I'm okay these days with fried rice too but when I was younger, I stuck to the brown rice.
Find whole grain breads you are willing to eat. Try different brands.
I now eat French bread periodically without issue but I've avoided white sandwich bread for decades. It's awful stuff that tears up my gut and my blood sugar.
I trend towards flat breads (recipe for one) or very, very fresh breads made in the grocery store bakery the same day or from a pizza place or similar. Ethnic breads, including pita, corn taco shells and German rye bread work fine for me though you need to figure out what to pair with it because those flavor profiles don't typically go well with most "American" cuisine.
I used to keep some kind of kid friendly whole grain sandwich bread in the house mostly for the kids when they were little. I'm not a huge fan of sandwiches, though there are exceptions.
Generally speaking, if it's made with white flour or white rice, just keep looking. That's the next best thing to sugar without being called sugar.
Proteins
I grew up in a meat and potatoes family. Like a lot of Americans, a lot of my protein comes from beef and chicken, though I seem to eat less meat than average for an American and have researched vegetarian diets, among other things.
I like baked meats and meats sliced thin and made on a George Foreman Grill or similar.
I eat cheese pretty regularly.
I'm okay with organic peanut butter and occasional helpings of dry roasted peanuts, BUT don't go overboard. Peanuts and especially peanut oil is pro inflammatory and substantial research suggests diabetes is associated with inflammation.
I have a serious inflammatory condition and I have gone to great lengths to figure out how to eat a less inflammatory diet. This condition puts me at high risk for diabetes.
Over the years, my blood sugar has improved without me per se trying to fix it. My best guess is addressing inflammation is a large part of why it has improved.
If you learn NOTHING else from me, get this tattooed on your mind somewhere: NO peanut oil.
Peanut butter is okay in moderation. Peanut oil is Darth Vader's next door neighbor.
I also ate a lot of game meats growing up (squirrel, deer) because my father sometimes hunted. It's fine and worthwhile to consider adding to your diet if that's an option.
I'm not a big fan of pork. I do eat bacon sometimes and pepperoni. I'm sometimes a bacon fiend because it's a fat I tolerate well which may have little or nothing to do with diabetes per se. I misprocess fats and that's peculiar to my condition.
I don't eat a lot of beans, though snow peas seem better tolerated for me than most legumes. It's possible I have markers for a moderate version of a different genetic disorder and I just can't eat beans too frequently. This may be my weirdo biology and may not generalize for diabetes.
I read Diet for a Small Planet years ago and I don't worry about trying to get enough protein. Most Americans eat too much protein and are urinating out the excess.
Traditional vegetarian diets typically have the correct ratio of legumes to grains or similar. People on r/exvegans report not getting enough protein on a vegan diet but it takes a lot to screw this up. If you aren't vegan and if your vegetarian meals trend towards traditional vegetarian recipes and aren't being super creative and avant garde, this should not be a big concern for most people.
If you go vegetarian, read up on protein combining to make sure you have some basic knowledge. If you go vegan, you may need to educate yourself more rigorously. If you eat some animal products, you probably are okay.
Produce
I had a college health class and we had to do an exercise recording our diet and I learned that I don't really distinguish between fruits and vegetables. I try to get enough "produce" in my diet and it's often more vegetables than fruits. Fruits trend towards being sugary.
Apples are high in pectin and do good things for blood sugar. For raw apples, I prefer Granny Smith apples but if I'm cooking it, I eat a wide variety of apples.
Research shows that aloe vera does good things for blood sugar. If you have never found an aloe vera drink you like, keep looking. If you want to be adventurous, research recipes for cooking with it.
I trend towards eating cooked fruits and came up with my own apple quiche recipe as a low sugar, high protein version of apple pie. I do eat raw oranges and such, but a lot of fruit is just too sugary and too acid and cooking it helps.
I eat a lot of potatoes. New potatoes require little preparation and cook quickly and are more nutritious.
I personally tolerate potatoes and corn better than many other things and those are both big staples of my diet.
I like onions, celery, carrots, broccoli, cabbage, various kinds of peppers, spinach, lettuce, salad greens, dried fruits, dry roasted nuts as some of my staples.
Snacks
You can get good quality bagged popcorn these days and I do fine with potato chips or corn chips. READ LABELS. You want something that says something like "Contains potatoes, salt and oil." If the ingredients list is longer than that, it's often a problem.
I like Ruffles potato chips and I like Cheetos and I like organic or simple versions. I do sometimes eat Doritos but I mostly avoid flavored versions of things because most of the time it's got something problematic.
I also sometimes eat pretzels, dried nuts, seeds, dried fruit.
Meal Frequency and Other Details
When I was younger, I ate small amounts frequently. That's a best practice for keeping blood sugar levels stable in a dysfunctional body.
I used to eat a high protein bedtime snack. If my mother made roulade, I frequently had leftover roulade and potatoes at midnight. If not, something involving cheese or eggs.
For desserts, I trend towards "rich" foods rather than super sweet. Very dark chocolates have little sugar. I sometimes eat cheesecake. I mostly avoid things like cookies and when I do indulge, it's like usually one or two at a time.
Last, while I live on Diet Coke, other than Diet Coke, I rarely eat anything using sugar substitutes. I just avoid sugars.
There is research that suggests artificial sweeteners do a lot of damage and promote weight gain.
I drink unsweetened tea or coffee or add a little sugar these days. I don't ever put artificial creamers or artificial sweeteners in them. Full stop.