Your lunchbox needs a vinegar soak and a day in the sun

The secret to killing onion and tuna smells is an acid wash plus full drying, not just soap and water.

Soap and water only clean the surface. Onion and tuna oils get trapped in the tiny scratches and pores of plastic, and those oils are what keep reeking. To break them down, fill the box with white vinegar and hot water (about 1:3) and let it sit for 30 minutes to an hour. Rinse and wash normally.

Then dry it completely — lid off, upside down, give it several hours. Smell loves moisture, and a dry box is a less smelly box. If you can, leave it in direct sunlight for a few hours. UV light kills the bacteria that make odors worse, and it’s genuinely free.

Still haunting you? Make a thick paste of baking soda and water, smear it inside, and leave it overnight. Wash and dry. If you get to that point, you might also consider just using a glass or stainless steel container for tuna/onion days. Plastic always holds onto some memory.

No one wants a tuna ghost haunting their sandwich.