From the blog:
Mr. Abrams the coffee maker. If you take the lid of a .50cal ammo box and pound the side lips down, you can slip the lid into the back grill of the exhaust. Then set your canteen cup for about 2 minutes. Let the 900 degree exhaust of your jet engine heat that puppy up and BAM - hot water for shaving, Ramen noodles, coffee, washing your face, etc.