For a bass you'd need a bigger can! I've heard of someone making a bass out of a 55-gallon oil drum but that's probably overkill, heh. I've seen some four-string washtub basses, though... here's one though it's an old page with very small pics:
http://dennishavlena.com/kochbas3.htm
And a different one Eldery used to have:
http://www.elderly.com/items/110U-3893.htm
It wouldn't be hard to do that kind of thing with a BG-scale neck and a pickup.
I also remember some resonator mandolins made from bedpans. Can't find those right now, but here's a bedpan guitar:
http://www.cigarboxnation.com/photo/...-bedpan-guitar