At that point the question becomes how do you cook without your normal fuel source? There’s a number of options for food prep that don’t consume normal fuel.
The most obvious is of course the plain old campfire. As simple as it sounds, it can actually be somewhat difficult to cook over a fire. It’s easy to burn stuff, so you have to be careful. Of course even burned food that was cooked over a campfire usually tastes better than normal…
The neat thing about campfires is that you can usually find fuel lying around and they’re pretty straight forward to start once you learn how.
Another option that’s similar to a campfire is a rocket stove. They are a specially designed stove that concentrates the heat from a small fire into a smaller cooking area. They get really hot with a fairly small amount of fuel. You can literally run these things on twigs and leaves if need be.
You can make a makeshift rocket stove called a “hobo stove” using a tin can as well … doesn’t take much work and I’ll write a how-to in the future.
Another decent option is a solar oven. They’re basically a box with a transparent or translucent window that lets light in. Set it out in the sun and it gets pretty hot. Hot enough to bake bread, cook a roast, etc.
You’ll have to have one of these on hand though. You can make one out of a box and tin foil, but it won’t be as effective as one that you bought.
So there’s three decent options for cooking without a standard fuel source. What are your favorites that I didn’t list?