When buying refrigerated or frozen foods from Trader Joe's, place a 19-cent frozen water bottle from the store in your bag of groceries to keep them cold as you make your way home.

Frozen water bottles act well as ice packs because they contain frozen-solid blocks of ice, which melt slower than ice cubes, keeping your perishable groceries chilled as needed.

However, if your local TJ's doesn't stock frozen water bottles, simply freeze your own water bottles and leave them in a cooler in your car, ready to help your groceries stay cold.