Bleach kills cooler mold best.

Yes, bleach. But don’t just pour it in. Mix about a tablespoon of bleach per quart of water, scrub the inside with a sponge, let it sit for 10 minutes, then rinse like crazy. Let it air dry completely with the lid open. That smell is temporary.

Vinegar and baking soda work okay for light mildew, but if you’ve got black mold spots or that musty smell that won’t quit, bleach is the only thing that reliably kills the spores. Just don’t mix bleach with anything else — especially not vinegar (toxic chlorine gas).

Rinsing is the step people skip. If you leave bleach residue, your next batch of drinks will taste like a swimming pool. Rinse until you don’t smell it anymore.

Let that cooler dry with the lid open for a full day. Mold loves moisture.