Have you tried Pu-erh tea? I find that it's very pleasant on my stomach and system as a whole.
Discussion
I haven't tried it, my regular is gunpowder green which is really tame on me. But I do make mine British with non-dairy creamer and Ripple which is a pea protein drink that tides my system over until I eat mid day.
I'm more Chinese style, small pots and cups, with lots of short steeps. It's incredible to experience how the flavor changes over a litter of boiled water. Takes about an hour to drink.
Lol, I make a quart mason jar full and have a hot water kettle I am constantly topping it off with. I end up drinking at least half a gallon each morning over 4+ hours but it's mainly water so good for hydration.