Take it apart. That's the whole trick.

Take the lunch box completely apart and dry every piece separately — that’s how you get mildew out of the hard-to-reach spots.

Most lunch boxes have removable rubber seals, plastic dividers, and latches that snap off. Pop those out. That’s where the pink or black gunk lives — in the grooves under the seal, around the hinge, in the little drain channel. A quick wipe on the inside won’t touch it.

Wash the pieces in warm, soapy water, then use a bottle brush, an old toothbrush, or a pipe cleaner to scrub the cracks and channels. If you see actual mildew, make a paste of baking soda and water, scrub it in, let it sit for 10 minutes, then rinse. Vinegar also works fine and kills spores, but rinse afterward so your lunch doesn’t taste like a salad dressing.

Then — and this matters more than the soap — set every piece out to dry completely before reassembling. Leave the box open overnight. Mildew only grows where moisture sticks around. If you put it together while it’s still damp, you’ll be doing this again in two weeks.

Mildew needs moisture, so dry time is your best friend.