Get a marble or a pebble, a big bowl, a coffee mug, and some shrink wrap. Put the mug in the middle of the bowl, and pour water into the bowl without spilling any into the mug. Cover the bowl with plastic wrap and place the pebble on the film in the middle. Put it in the sun and let condensation do the work.
Grab some sand, two pots (big and small), and a washcloth. Put the smaller pot inside the bigger one, fill the space between with wet sand, and cover with a washcloth. Finally, put the food inside the smaller pot.
Get a coffee can, a toilet paper roll, and some rubbing alcohol. Maneuver the toilet paper roll to get the cardboard out without unrolling it. Then collapse the paper so there's no space in the center. Put the roll in the coffee can, soak with rubbing alcohol, and light it on fire.