Very hot coffee — with plastique

C4 is a common military plastic explosive that, according to Wikipedia, detonates at a velocity of nearly 30,000 km/h. If you don’t use a blasting cap or detonator to set it off, though, you can light it with a match and it will burn.

This guy says you can use spitball-sized pieces of C4 to heat up your coffee:

As one ball would burn out, you rolled another up next to it, so it would ignite.  We used a modified C-ration can for a stove.  One side was cut open, so there was plenty of air for the ‘rapid combustion.’

The trick, apparently, is not to stamp out the fire.