What should I use to clean a moldy cooler?

Bleach is the move for moldy coolers. Scrub with dish soap and hot water first, then apply a bleach solution (one tablespoon per gallon of water) for 10-15 minutes, and rinse thoroughly. Don’t mix bleach with anything else — especially vinegar, which creates toxic chlorine gas. Let the cooler dry completely with the lid open before storing.