Walmart sells 'water bladders' for like $10. That's what I use in my backpack...much cheaper than a camelbak and if it gets nasty just buy a new one. I fill it about 3/4 full with water and throw it in the freezer the night before the ride. They tell you not to use any sport drinks in them..I'm guessing they can grow stuff if you don't clean them out well. I clean mine with baking soda and water, then lemon juice, then rinse it clean. I usually store it empty in the freezer, too. Last thing you want is diarrhea on a ride b/c your camelbak was growing some nasty bugs.