Silicone muffin cups fix most lunch leaks.

Silicone muffin cups are the cheapest fix for a leaking lunch box, and freezing your yogurt solves what’s left.

The main rule is never pack wet food loose. Even a decent lunch box will slosh. Put yogurt, fruit salad, and applesauce in their own small containers with locking lids — the kind that seal on all four sides, not a snap-on lid. Test any new container once by filling it with water, closing it, and flipping it upside down over the sink. If it doesn’t sweat, you’re good.

Sliding happens because smooth plastic against smooth plastic has no grip. Drop a silicone muffin cup into the lunch box and set the container inside it. The silicone grips both surfaces, and it doubles as a divider so your grapes aren’t rolling into your sandwich. If you don’t want to buy anything, wrap a rubber band around the container a couple times. Same effect, slightly uglier.

For the wet stuff itself: freeze the yogurt. A frozen cup keeps the whole box cold and thaws by noon without making a mess. Fruit salad is the exception — freezing ruins the texture. Drain the juice before packing, because the juice is what leaks. Put it in a tiny separate container if you want it back, or just accept slightly drier fruit.

Thirty seconds of prep beats cleaning yogurt out of a backpack.