Bleach is the only thing that reliably kills lunch box mold

Bleach is the way to go for mold in silicone seals — soap and vinegar just won’t get it done.

First, take the whole thing apart. Silicone seals usually pop right out, so remove every piece you can. Then soak all the parts in a dilute bleach solution: about a tablespoon of bleach per quart of cool water. Leave it for 10–15 minutes. This kills the mold rather than just scrubbing the visible parts away.

For the crevices that won’t come apart, use a toothbrush or a pipe cleaner dipped in the same bleach water to work into the corners. Silicone is fine with boiling water too, so you can pour boiling water over the seal after the bleach soak as a final rinse — it breaks down any grime the bleach softened.

Skip the vinegar. It’s okay for a bit of surface fuzz, but mold that’s wedged into a crevice has roots, and vinegar doesn’t kill roots. Also skip soaking the whole plastic body in bleach for long if you’re unsure about the plastic — but the seals and removable bits can take it fine. Just rinse everything thoroughly with hot water afterward.

And once it’s clean and dry, stop closing the lid all the way when you store it. Mold needs damp, and a sealed lunch box is a damp cave. Leave it open for a few hours after washing, every time.