For rides to the grocery store I can get away with just one bottle of water. I can always top up at the store if I need to. Such rides aren't exactly workouts, although riding the hybrid feels like hard work after being on the road bike.
For weekend rides of more than one hour, I get out the CamelBak. The one I have is 100-oz capacity, usually enough for several hours of riding. I've never put anything but plain water in it, to make cleaning easier. Performance Bike offers a cleaning brush kit, and that "snake" sure makes cleaning the drinking tube much easier!
All this thinking about CamelBaks has gotten that old song running through my head: "...you're never gonna see no unicorn."