Actually, one of the best ways to rehydrate is as follows:

1 litre of water
1 teaspoon of salt
8 teaspoons of sugar

This is common knowledge in tropical countries where cholera is pretty common. I've heard it's much more efficient than gatorade or any other sports drink at getting fluid levels back up (which is good, because a bad case of cholera will have you ****ing 20 litres of fluid a day)

Doubt its any good for an upset stomach tho