Whoever came up with the idea of carrying potable water within your backpack is or was a genius, that's all we have to say on the matter. Other than that you can make sure that you're kept hydrated the whole day long with clean and safe water with one of these backpacks from such great brands as Osprey and Camelbak.
Camelbak M.U.L.E. 100oz Hydration Pack 62394
Camelbak Fourteener 24 100oz Pack 62191
Camelbak Fourteener 24 100oz Hydration Pack 62369
Camelbak Pursuit 24 LR 100oz Hydration Pack 62426
Camelbak M.U.L.E. 100oz Hydration Pack 62395
Camelbak Women's Spire 22 LR 100oz Hydration Pack 62461