Stainless steel is the answer.

Stainless steel lunch boxes are the best plastic-free option for kids — light enough, basically indestructible, and easy to clean.

PlanetBox and LunchBots are the two brands to know. PlanetBox makes those compartmentalized metal trays that look like a grown-up bento box; they’re pricey but kids love the sections, and they survive years of being thrown in a backpack. LunchBots makes simpler stainless tins that cost less and do the same job. Both are dishwasher-safe, which matters more than you’d think.

You’ll want to skip glass, even the “shatterproof” kinds — too heavy for a kindergartner’s bag. Bamboo is lightweight but it warps and cracks, and most bamboo lids still use plastic seals. And avoid anything labeled “wheat straw” or “plant fiber”; that’s usually plastic composites dressed up with green marketing.

The one honest exception: silicone snack bags like Stasher work great for sides, and you can fold them into the main box. But for the box itself, steel wins. It doesn’t absorb smells, it doesn’t stain, and it’ll still be in good shape when your kid outgrows it.

PlanetBox is the splurge; LunchBots is the smart buy. Either one beats another plastic package that breaks in nine months.