First you need to get a hold of two botte caps, preferably the same kind. If they are a bit bashed up, bash them in to shape with a hammer. Make a small hole in the top, center of each cap with a stanley knife.
Slip jump rings through the holes on the caps.
Cut two short lengths of chain and slip the chains on to the jump rings.
Attach another jump ring on to the top of each chain and add an earring hook. Close the hoop and run off to the pub to show your friends.