I have built some survival kits based on a water bottle before. I agree that the best thing to put in a water bottle is water, but it is a good container. I would include something like this:
Sea to Summit Day pack

the older model packs even smaller

Or:

Kiva Key Chain Backpack

If you can find it anymore.

Just to have somewhere to transfer everything when you do put water in the bottle.

I do prefer the stainless steel single wall water bottles as well. They do fit in the same pockets as the plastic Nalgene bottles, and inside the space saver cups. Just more capable and allow use in a fire. I have several.