A water-resistant emergency kit
So granted you'll have to drain this in an unorthodox way, but here's proof that beer can actually save your life -- and not in that pseudo-science-y, fake study type of way. Without popping the tab, cut a hole in your beer (like you're about to shotgun it!) and make a little door. Drain the beer out, and fill it with anything you might need in an emergency: BAND-AIDS, matches, condoms, etc. Then, tape up the door with duct tape. With this hack, the entire plot of Hatchet wouldn't happen, and fourth-graders would have nothing to read this summer.
A Wi-Fi booster
This sounds like something stupid your dumb cousin tells you, then when you ask him to back it up, he just yells, "Google it!" Well, as it turns out... this is actually pretty valid. By ripping up the foil of your cans, and wrapping them around your router's antennae, you can improve your signal a lil' bit. You can also use tin foil to do this... but there isn't normally beer in tin foil. So, beer cans are an obvious choice.