You were asking about a hydrating drink so here is one to try. I used it when on clears before my pouchoscopy this time and didn't feel so drained from losing electrolytes like I usually do. Its worth a shot anyway and isn't too expensive.
the juice from 1 lime
1 splash of cider vinegar
a pinch of sea salt (I used the pink Himalayan sea salt)
1/2 t. of stevia
add water to fill your cup. (I used a 32 oz. big cup.)
stir around and sip