Context is I’m fasting for health reasons, rather than weight loss so aiming to minimise insulin response. I can drink plain green tea, but my favourite non-black teas have always been jasmine green tea and mint tea (either with green tea or just mint). I usually drink something like this, where the ingredients are 100% green tea. https://groceries.morrisons.com/products/morrisons-touch-of-jasmine-green-tea-250876011
Lots of fruit/ herbal teas have things like fruit pieces and flavourings, are these ok to drink when fasting? I can’t stand liquorice flavours so avoid anything which uses that for sweetness anyway, if that would be a problem.
How about mint tea like this one, where the ingredients are different kinds of mint? https://groceries.morrisons.com/products/pukka-three-mint-organic-herbal-tea-with-peppermint-spearmint-20-sachets-268624011
For health reasons, the best choice is to go as minimal as possible. For example some herbal teas can be harsh on the digestive system or at least stimulate it and a lot of people want to maximise bang for buck.
That being said it should make little difference if you tolerate them. Depends how much you want to squeeze out of this fast.
I always think if you’re doing it for health you don’t have to do it frequently so maximise the time when you do it.