There are a fair few tutorials about on the net showing how to make little wallets or purses from used tetrapack containers. My kids love the occasional chocolate or vanilla milk, so I thought it would be cute to make them a wallet each from one of thier drink boxes.This site sells recycled tetrapack wallets, but you can see the process of how to make them from the little animation on the front page there. It's quite simple and if you weren't in quite so much of a hurry as we were then you could use a little velcro or a snap closure on them instead of the rubberband we used.
I bet you could make a nice grownup scale one with a soup size tetrapack. Might be nice for keeping scraps of paper with recipes on in.