I use Slippery Elm Bark powder - not often, only when I need it, but it works for me. It was recommended to me by a natural therapy professional about 40 years ago.

Caution, if I mix hot water with the powder I always put a heaped teaspoon of powder in a cup, then 1/3 cup boiling water, quickly mix it up and immediately put stir in 1/3 cup of cold water. If you try to drink it with boiling water you could burn your mouth because it retains the heat too well.

It has little to no taste, but lemon juice or honey could be added. I only make 2/3 cup because I don't mind the taste, but you could make it a bit more watery.