When I was in elementary school we used to open it all the way up and fold in, so it was just like a square cardboard cup. We called them Jimmy's Coffee Cups, after our awesome janitor (imagine the janitor from scrubs, but older). We got in trouble for some reason from our principle for "demeaning" him, but Jimmy told us that he secretly appreciated our tribute, and from then on he actually used those for his coffee
Ahh, the memories.