Plain black tea with nothing added raises my blood sugar :( I refuse black coffee. Anyone else can’t do black tea?
https://insulinnation.com/living/why-coffee-raises-your-blood-sugars/
Green tea has a fair amount of caffeine too, you may want to stick to water.
I enjoy green and black tea but cannot do either on an empty stomach. Oddly enough, they raise my blood sugar when I’m fasted, but if I’m in my eating window (but a few hours after eating) and have some, it has no notable effect.