For disaster preparedness or on a camping trip, here are three options to boil water quickly using a small and well contained fire. Whether it is to boil water for a cup of coffee, or to prepare a freeze dried meal, a Thermette, a Kelly Kettle or a Hobo Stove are all great options in the outdoors. Here is a short demonstration video on using them. Each of them can also be used to cook meals as well.
They are very economical on fuel ( wood, dried grass, leaves etc).