Baking soda and sunlight will fix that lunch box.

Baking soda is your best bet for a smelly plastic lunch box, but sunlight does the heavy lifting.

Wash the box with dish soap first to get rid of grease and food residue. Then make a thick paste with baking soda and a little water, spread it inside, and let it sit for thirty minutes or overnight if it’s really bad. Scrub gently, rinse, and you’re done. Baking soda is mildly abrasive but safe on plastic, so don’t worry about scratching.

Vinegar works too, but you’re just swapping one smell for another. A 50/50 vinegar-water soak kills bacteria and neutralizes odors, but that vinegar tang can linger in cheap plastic. If you use it, rinse thoroughly, and maybe follow up with baking soda or dish soap.

The real trick is sunlight. UV rays actually break down the organic molecules that cause smells. After cleaning, put the box in direct sun for a few hours—inside out, lid off. That kills most lingering odors that washing can’t touch. Just don’t leave it out all day for weeks on end; prolonged UV will make plastic brittle and faded.

For really stubborn smells, repeat the baking soda and sun cycle. If that doesn’t work, the smell is probably baked into the plastic itself, and it’s time to replace the box.

Your lunch box will smell like nothing, which is the best smell.