Coolers
From Burnwiki, a Burning Man Wiki & Brain Dump
First off, styrofoam coolers suck. They break and create lots of little white styrofoamy MOOP. Bring a real cooler. If you're flying in, a cooler can even be packed with gear or clothes, and used as luggage.
Ice is available at Camp Arctica so you can refill your cooler daily to keep any beer cold and perishable food edible. It's also possible to create a deep freeze by using dry ice, but this is risky. Air leaks, accidental placement of coolers in the sun, and frequent access can make your otter pops melt far before the man burns. Regardless of how you're cooling your cooler, keep it out of the sun. All of that insulation is no good against the sun at high noon.
