drinking water is important, that is how we detox out shit, howeveri think the fluid thing has been blown out of proportion by the sports drink companies who cherry pick studies.. well I don't think, i know.
the fact is a lot of athletes actually drink too much water. i was guilty of this when i used to run and it cost me time off my runs. you want to make sure you are properly hydrated but drinking too much is not necessary.
what i do is urinate before my workouts, if it isn't clear i drink a bit more and when i get thirsty i sip during.. as simple as that
drinking water is important, that is how we detox out shit