Just being poetic, all three of these methods yield acceptable coffee, the main objective being caffeine --> bloodstream.
My favorite method for brewing coffee on the go is what I've always referred to as a cuban espresso pot, which actually is manufactured in Italy. I did learn about this from Cubans in the Florida Keys, and I actually bought this unit in a local grocery store for twelve dollars. Just add water, coffee, and a flame. Good coffee!
The easiest method to procure quick coffee is instant coffee and hot water. The brand pictured is the one I prefer. This is also very useful for raising the octane when you are forced to swill a weak gas station cup o' Joe.
My quick and dirty method for brewed coffee is to fold a funnel out of a bandana, or other relatively clean cloth, add your grind to the depression, then slowly pour hot, but not boiling water until desired strength/volume is achieved.
I once read that coffee inflicts a sense of urgency similar to the rush a small animal experiences when chased by a larger animal. I know I enjoy it!