depends on the temperature.

if it's 80+° then i'll easily go through a .5L bottle every hour (although if i'm feeling overly hydrated i'll just swish and spit on occasion), especially if it's a long ride.

i'm a sipper, which means i'll take water every few minutes, in small shots. probably picked that up from Eddy Bs book where he warns against drinking too much at once and having the water slosh around in your stomache.

on a day like today, where i went out for an easy hour and a half in temps that were in the high 60s, then i only drink half of a bottle.

tomorrow i'll be doing a race that will last about as long as todays ride, and most likely i'll come close to going through the entire contents of my .75L bottle.

btw, fwiw, i always drink water, never gatorade, or other mixes.