I heard smoking out of aluminum cans are pretty bad for your health, because of the fumes given off by the metal...but I've done it once or twice. Apples work pretty good if your in need of a piece, and like the other dude said, the taste is decent.
You can make a bong out of absoutely anything!
I find that the most random shit around the house is the most rewarding in the end, when the final piece is complete...and you feel like McGiver! haha!
The best makeshift bong I've ever made was with a 20oz Powerade bottle.
1. Poke a hole in the side of the bottle, about 2 inches above the bottom.
2. Stick a straw through the hole.
3. You can tape the hole up, or you could try melting it closed, main purpose being to keep it airtight.
4. Connect a trumpet mouthpiece or some other metal bowl shaped instrument at the end of the straw poking out, aluminum works well, but be sure to change the bowl piece regularly if you go that route.
5. Poke another smaller hole towards the top of the bottle, for the carb.
6. Pack the bowl, toke, and enjoy!
The carb isn't exactly necessary, but I find that it's a harder, longer hit. And plus it's just more engineering...lol.
Good luck!