My current setup is the bottom third of a 24oz beer can with about 8 tiny holes drilled around the bottom edge. It fits the top of my Camelbak Forge travel mug perfectly. I put a coffee filter into it, a few scoops of ground coffee to make a good cup of pour-over coffee.

A few years ago, I made a percolator to fit into my cooking pot out of beer cans:
http://www.bikeforums.net/touring/71...l#post12552867