For soup, get a gasketed clip-lid box, not a thermos

The best leak-proof lunch boxes for soup are the OXO Smart Seal and LocknLock, both with rubber gaskets and clip-down lids — skip the Pyrex lunch containers entirely if you’re carrying broth.

A thermos isn’t the only way to carry soup. It’s actually kind of a pain: narrow opening, hard to eat from, and it’s one more thing to wash. A good hard-sided container with a soft gasket in the lid does the job fine, as long as you seal it properly.

My top pick is the OXO Smart Seal. The gasket sits in the lid rim, the clips lock down firmly, and it’s genuinely leak-proof in daily life — people carry soup and curry in them all the time without bag disasters. It’s also microwave- and dishwasher-safe, and easy to open one-handed.

LocknLock is the budget champion. It’s the container every Korean mom uses to send soup to school, which is basically a century of empirical testing. Slightly flimsier plastic than the OXO, but it doesn’t leak. If you want glass, Glasslock’s airtight lids work too — just accept the weight.

Don’t trust Pyrex Snapware lids with thin liquids. They’re fine for leftovers, but they’re the #1 complaint in every “soup leaked in my bag” story I’ve read.

One rule before you pack any of these: cool the soup first and leave at least an inch of headspace. Warm liquid sealed tight builds pressure, and pressure is what turns a “leak-proof” lid into a leaky one. On airplanes, resign yourself — pressure changes have defeated every container ever made.

This is not where you save eight bucks.