This typically sugary childhood favorite may not be ideal for everyday consumption, but it can be a well-received treat at a birthday party, and it's an affordable way to quench your partygoers' thirst. For about $5 you can provide drinks for the whole group.
Powdered drink mixes come in lots of flavors, so you can mix it up by putting out pitchers holding a few different, brightly colored options, like fruit punch, grape drink and lemonade -- and maybe an iced-tea pitcher for the adults. You'll also want a grown-up stationed nearby for refills.
Frozen, fruit concentrates are a low-cost option, too, if you'd rather go the natural route.