I have been known to use the bottom three fourths of a cut-off one liter soda bottle. Nice thing about that is that you can pinch it enough to pour all the water into the small opening of the water bottle without spilling. It also protects the windscreen I made for my canister stove to keep it from getting bashed out of shape. I usually take the cut-down bottle only when one of the grandkids is with me, and he/she gets to carry it. When I'm alone, I use my cooking pot, which is usually close to the top of my pack. Out here in the western mountains, though, there's usually plenty of falling water--the pot is needed only for lakes.