A simple padlock works.

Yes, just get a small padlock and run it through the hasp that’s already on the cooler. Most decent coolers (Igloo, Yeti, Coleman) have a molded-in hasp or a metal loop specifically for this. If yours doesn’t, a small cable lock through the lid handle and a tie-down point works.

Don’t buy a special “cooler lock.” They’re overpriced and often the same as any luggage lock. A metal padlock is fine—just make sure it’s corrosion-resistant if you’re camping in rain. The goal isn’t Fort Knox; it’s to stop someone from casually grabbing your drinks while you’re at the stage.

A determined thief with bolt cutters will still get in, but that’s rare at festivals. This stops the opportunistic snatch-and-go.