Cola bottle babies. These securely hold around a 1/4 cup of emergency food like beans, rice, or oatmeal.
You could use them for dried fruits, granola, coffee or seasonings.
They could also securely hold a small amount of fuel, matches, tinder, money, small hardware or your medications.
Use these for anything that needs to be sealed. Once you seal and reopen the bottle the top ring will break like a soda bottle, however you can still open and close to use the container to keep your items, you just know which one has been opened.
Grab several of these for different purposes.