Baking soda and vinegar kill cooler mildew smell.

Yes, that smell is mildew — and it’s fixable.

Start by washing the cooler with warm water and dish soap. Scrub every surface, including the lid and drain plug. Rinse well. Then make a paste of baking soda and a little water and spread it all over the inside. Let it sit for 15–20 minutes. Scrub again, rinse.

Follow up with a 50/50 mix of white vinegar and water. Spray or wipe it on, let it sit for 10 minutes, then rinse thoroughly. The vinegar neutralizes the baking soda and kills the mildew smell. Let the cooler air dry completely — lid open, drain open — for at least 24 hours before storing.

If the smell lingers, you can use a diluted bleach solution (1 tablespoon bleach per gallon of water) but be careful: bleach can discolor plastic and leave a chemical smell. Rinse multiple times if you go that route.

Mildew loves moisture — never close a damp cooler.