2 gallons, WOW, I hope they keep a bladder bag nearby!!! Or some empty bottles, LOL! I usually get through about 3, 24 ounce sportpacks of water at work, and plenty of water at the gym water fountain, and I don't seem to look to bloated? I have heard that the colder the water, you can actually burn more calories, dont know if this HOLDS WATER or not, but!