I guess a lot of any liquid would temporarily distend the stomach and tighten the hiatal hernia? Sounds like you have a lot of experimenting to do and adjustments to make. Possibly eating lots of small snacks rather than full meals would help, though that would make managing your insulin doses more difficult? Rats!
I personally find mint teas very soothing, though as with anything, it'll take experimentation to sort out. Apple cider vinegar seems to help my digestion as well.
Good luck with it all, Adrian.