Freeze a wet sponge in a baggie

The easiest DIY ice pack for a lunchbox is a wet sponge sealed in a zip-top bag and frozen. It stays cold longer than most alternatives, fits around food, and doesn’t turn into a soggy puddle by the time lunch rolls around.

The trick is the sponge. Soak it, squeeze out the excess so it’s damp but not dripping, then toss it in a sandwich bag and freeze it flat. The water inside freezes into a solid block that thaws slowly, and the bag keeps everything dry. You can reuse it all week, and if you have a few, you can rotate them.

Frozen water bottles work too, but they sweat. A frozen juice box is fine if you want something to drink with lunch, but it’s not as cold. If you have a small container with a tight lid, freezing yogurt or applesauce gives you a cold pack and a snack, though it doesn’t stay as cold as a dedicated block.

Just make sure the baggie is actually sealed. You don’t want sponge-flavored ice water in your kid’s backpack.

Future you will thank Present you when nothing smells like tuna.