I agree -- you should absolutely have water in-hand, even if it's one of those 8 oz mini-bottles. (A pouch or box is useful one time, but I don't think you can easily refill them.)

Quarters are good, as philip said -- but in case it's not an emergency that overloads the mobile/cell system, you should always make sure to recharge your cell phone while you're sleeping.

Consider adding more bandaids ... if you have to walk long distances, and you're not wearing suitable footwear/socks, you'll get blisters.

Remember to periodically check the battery in any flashlight(s) you EDC.