Have you ever been in a situation where you needed a drink of water either for thirst or for something like taking a pill? Here is a solution, learn this once and know it when you need it. There is a high probability, wherever you are, that there is a sheet of paper nearby. Notebook paper, a pamphlet, a flyeror printer paper. Anything will do. You can then fill it at the nearest faucet.
This design will use a standard rectangular sheet instead of a square one. Similar to this