From LifeHacker--"Freeze Water Balloons to Keep Drinks Cold." Could be a less messy way to keep beverages cold for graduation parties.
To keep your drinks cold and your party festive this summer, fill balloons with water and freeze. It's cheaper than ice from the store and you won't have to worry about sticking your hand into water cold enough for cryostasis just to get your beer in the bottom corner of the cooler.
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Fill balloons with water, freeze and use and reuse them instead of ice bags.