These can be made to hold anything from tea, sugar or coffee to spices, medicines, little fishing kits and anything small enough to fit inside.. Mostly they are used to contain fire making materials like cotton wool and Vaseline..
all you need are straws, a pair of pliers and a lighter plus whatever you're going to be putting inside, in this case, cotton wool and Vaseline
pinch the end of the straw flat and melt it with the lighter, it forms a waterproof seal very well
mix your Vaseline and cotton wool and stuff into the straw with a bamboo skewer or thin stick
once done, pinch flat the open end and seal with the lighter
job done, and you can use any thin tubular items to do the same job. They are waterproof, they float and once opened the straw also becomes a source of fuel when burnt along with the cotton wool giving you valuable extra time for the fire to catch.
( These straws came from subway, they're a good size diameter, though you can get really good ones from KFC when you get a crushem.. they're nearly1/2" in diameter!!)