Take the gasket out. That's where the bacteria lives.

The single most important step is removing the rubber seal and washing it separately — that’s where moisture and crumbs hide and where the real buildup happens.

For daily cleaning, hot soapy water and a quick scrub on every surface is fine. Use a bottle brush or an old toothbrush for the corners and the channel where the seal sits. Don’t just rinse — actually scrub. Then dry it completely with the lid open, upside down. Bacteria needs moisture to multiply, so a dry lunch box is a safe lunch box.

If it’s dishwasher safe, you can run it through the machine, but check first — some plastics warp on the bottom rack. Hand washing is always gentler and often more thorough for those corner seams anyway.

For weekly sanitizing, wipe the whole thing down with diluted white vinegar or a bleach solution (about a tablespoon of bleach per gallon of water). Let it sit a couple minutes, then rinse thoroughly. For persistent smells, leave a baking soda paste on the inside overnight, rinse, and let it dry fully.

Also worth noting: most lunch boxes don’t have a removable seal, and if yours is permanently attached, you need to be extra diligent about prying the edge open and cleaning underneath with the brush. If it’s moldy or stained and won’t come clean, replace it. Don’t fight that battle forever.

Future You will appreciate not eating near something that smells like last Tuesday’s tuna.