I know I am a little late in offering my humble inpit and maybe better late than never.
Didn't read all the posts but many and agree with the concensus; would like to add one thing.
It is generally the loss of potassium with liquid stools that causes the symptoms of body ache, fatigue, weakness, headache in the absence of other problems like fever, or something more serious than mild food poisoning or flu.
So Gatorade is OK as is a salt and sugar mix but these offer more sodium than potassium and will not releive the symptoms mentions
A few capsules of a potassium salt can make all the difference, avaiulkable at any heath food store, Vitamin Cottage, Whole Foods, probably at Wal Mart and target or a pharmacy too.