You need two ice packs, not one

To keep a lunch box cold for eight hours without a fridge, you need an insulated bag and two ice sources — one under the food and one over it. That simple trick beats any single ice pack, no matter how fancy.

Cold air sinks, so a lone ice pack at the bottom only keeps the bottom of your lunch cold. The stuff near the top of the bag warms up fast. Put one frozen pack under the food and another on top of it, and you create a cold sandwich. That’ll easily get you through an eight-hour day.

Your best cheap ice source is a frozen water bottle. It lasts longer than most gel packs, thaws into drinkable water, and costs nothing if you’ve got a freezer. Freeze two the night before, pack them around your food, and you’re done. Also: pre-chill your lunch box itself and cold food before packing. And pack it full — empty air is what warms everything up.

If your bag is flimsy, upgrade to something insulated. That matters more than the ice pack does.

Future You deserves a lunch that doesn’t taste like a gym sock.