Soak it. Scrubbing alone won't kill the mold.

Mold in the seams of a lunch box needs a soak in a cleaning solution, not just a wipe-down — then a scrub with something thin like an old toothbrush or a pipe cleaner.

Soap and water won’t cut it here. The mold is hiding in the grooves where the lid meets the base, and you can’t reach it with a sponge. Fill the box with hot water and add either a cup of white vinegar or a tablespoon of bleach. Let it sit for 15 to 20 minutes. That soak loosens the mold from the crevices, then the toothbrush and some dish soap finish the job.

Rinse well, especially if you used bleach — you don’t want that residue near food. Then dry it completely, lid open, for a few hours before storing. A dry lunch box doesn’t grow mold, so that last step matters more than the cleaning.

If the box has a fabric lining or Velcro, check whether it’s removable. If not, vinegar is gentler than bleach and still does the job. If the mold has been there a while and you can smell it after cleaning, toss the box. Certain materials just absorb it.

And from now on: dry it with the lid off after every wash. That’s the whole trick.