It is possible to boil water in an unwaxed paper cup without the cup
igniting. Pour water or milk into the cup. Cut a small square of
aluminum foil and place it under the cup. Set foil and cup in or on
the hot coals. The foil protects the small lip on the bottom from
burning. If flames rise against the top of the cup where liquid does
not reach, the cup can burn.
You can also hard-cook eggs in a paper cup. It is also possible to heat a
carton of milk if the carton is unwaxed. Open the milk carton top