You may find that aspartame and other artificial sweeteners or sugar alcohols (xylitol, maltitol, etc.)cause a glycemic reaction. I get migraines from aspartame, and a glycemic reaction from the sugar alcohols because they still contain sugar though a lesser amount.
Water and tea are your best bets. You can add a squeeze of lemon or lime juice to the water to add flavor. One thing I do if I am really craving a "soda-like" drink is put 1/2 inch pomegranate or blueberry juice in the bottom of a glass and top it up with club soda/sparkling water. The strong juice gives a really refreshing taste, but the small amount doesn't spike my blood sugars. You could add it to still water as well, but don't get carried away and put a lot of juice in. Even an ounce could cause a glycemic reaction.
Try herbal teas that have a fruit-like taste like orange spice.
For the most part though, you should just drink good old water.
Avoid any teas with caffeine totally. There are lots of herbals though, as suggested, that taste great. Juices can actually be okay if you know what to get. Try starting with bitter berry juices (cranberry, blueberry, etc.) and cut with equal water to see how you do. Also look at unsweetened almond milk, I like it. You may also want to look into the RAW form of Stevia. This has to be purchased at a health food store, don't get any of these new fangled fad Stevia products they've been making. Stevia is a green powder. You can also get it refined, which is much sweeter, but still okay for you. Raw is better because of the phytonutrients.
Very interesting. Yes I agree. The first thing most of us do is avoid sugar and use sugar free products instead - which usually contain aspartane. But my diabetic husband was diagnosed with aspartane poisoning and was strongly advised to avoid it totally. I also stopped using all aspartane products and found my blood sugars stabilised. Its best to avoid all sugars but real sugar is better than aspartane (for me anyway).