I read a comment by a runner at blog or magazine, "(At a race) I dilute Gatorare in half." In fact, that is a good way of intake efficiently at the osmotic pressure point of view. It is quiet between fluid A and fluid B if they are same density. So if we need to make the one lower than the other (in this case, let's make sports drinks lower), a body begins to absorb it. It seems that an ideal concentration is the one of oral rehydration salts.
For me, who have Chemistry major, it reminds me old days in lab... (sigh).