When I’m really PMSy, I’ll sometimes buy a Zevia (stevia/erythritol soda). They’re not even that good…my uterus just has really strong feelings about carbonation :p
That said, they contain citric acid (sometimes corn- or yeast-derived), erythritol (calorie-free sugar alcohol, debate over whether it’s suitable for people with digestive issues), and “natural flavors,” whatever that means. They don’t seem to affect me adversely, but I certainly don’t actually suggest anyone drink this crap. I also waited until I was pretty far along in my progress before ever trying one.
I personally don’t think organic green tea is terribly problematic, but it would behoove you to monitor any differences you feel when you drink it.