Soup belongs in a thermos. Yogurt needs a locking lid.

The only truly leak-proof way to carry soup is a vacuum-insulated thermos, and for yogurt, a container with a rubber gasket and locking clips works better than any screw-top jar.

Thermoses use a two-part seal: a rubber stopper on the inner lid and a screw-on outer cap. That’s why they survive being tossed into a backpack. The vacuum insulation is a bonus — you get hot soup or cold yogurt for hours. Brands like Thermos, Stanley, and Zojirushi all make wide-mouth versions that are easier to fill and eat from.

For yogurt, skip jars and cheap plastic deli containers. Look for containers with locking tabs on all four sides (think Rubbermaid Brilliance, Pyrex Snapware, or Bentgo). The tabs press the lid down around a silicone gasket, which creates the actual liquid-tight seal. Whole Foods plastic tubs with a press-on lid are not in the same league. When a container says “leak-proof,” test it before you trust it: fill it with water, close it, turn it upside down, and shake it hard. If it stays dry, it’s backpack-worthy.

One note: “airtight” and “leak-proof” are not the same thing. Airtight keeps flavors in; leak-proof keeps liquid in. Read the label carefully.

Yogurt and soup are two of the worst foods to clean out of a bag. Spend the extra few bucks on something with a real gasket.