They are great for storage of small items, like these buttons (or in workshop for nails, nuts and bolts)
Or to sort plastic lids
I even use my leftover cups to submerge my paper beads. When I'm done I simply snap the lid on and cover the straw opening with a piece of tape to keep my leftover adhesive and varnish as fresh as the day I poured it into the cup. These would be great for storing leftover kids paints too.
Do you reuse your beverage containers for anything else?