I remember having a really nasty stomach bug in brazil and they gave me coconut milk (straight from the coconut) which was quite horrible but, don't know if it was co-incidence but after that I began to improve quite rapidly. Not an easy thing to get hold of though. I have heard of the flat coca-cola as well, it's easy to get rid of the fizz, just shake it up, gently let some of the fizz off through the top, and continue to do that until all the fizz has done, doesn't take long.