Y'all, or whatever:

Water in aluminum foil should keep the foil cool enough so that it does not melt, because the water needs 212 degrees F to boil, and aluminum foil needs a bit more than that to melt. I am assuming you are using a regular fire and not an acytelene torch which would definitely melt the area it hits as the heat gain will be greater and faster than the heat loss capability of the water.

I have heard, and seem to recall having seen one instance of water being boiled in a paper bag. The only downside of that is the physical integrity of wet paper. You could fill a paper bag with water, and use any hole riddled aluminum foil as a support mechanism. I would imagine that with rapid emptying of the bag after boiling the water, you could use the bag again until the wetness of the paper finally causes the bag to disintegrate.

Bountyhunter