Bleach and water. Nothing else.

Dish soap removes grease but doesn’t kill all the bacteria from raw meat. The only reliable way to sanitize a cooler after raw meat is a diluted bleach solution — 1 tablespoon of unscented bleach per gallon of cool water. Wipe down all surfaces, let it sit for a few minutes, then rinse thoroughly and let it air dry completely with the lid open. Skip the vinegar and baking soda gimmicks. They smell better but aren’t as effective against salmonella or campylobacter.

If the cooler is really stained or smells, a paste of baking soda and water can help after sanitizing, but that’s cosmetic. The bleach step is the one that matters.

Future you (and your next picnic) will thank you.