A screw-top food jar is the only real answer.

If you’re carrying soup or stew, skip the pretty bento boxes and get a screw-top insulated food jar.

The whole “leak-proof” latch-and-clamp lunch box category is a lie. Bentos with side clips look great in ads, but the seal is a flat gasket pressed shut by plastic tension. It works for a sandwich. It does not work for hot broth bouncing around in a backpack. One dropped bag and you’re cleaning soup out of everything you own.

What actually works is a threaded lid — the kind you twist on, with a silicone gasket inside the rim. That’s why thermoses have been spill-proof for a hundred years.

Two worth owning:

• Zojirushi Stainless Food Jar — best insulation, best seal, pricey but bulletproof. This is the one I’d buy again.
• Thermos Stainless King Food Jar — cheaper, slightly less precious, same screw-top reliability.

One rule regardless of which you get: don’t fill it to the top. Leave an inch of headroom. Hot liquid builds pressure and a full jar will push past even a good gasket. Fill it three-quarters, screw it down, and turn it upside down over the sink once before you leave. That test settles it.

Your bag’s lining will thank you.