With summer barbecues and backyard parties around the corner, the inevitable question comes up: What do you do with leftover beer? When stuck with half-empty cans or bottles, consider trying this reuse idea: Use the beer to attract butterflies. Mix stale beer with sugar and pour it all over your garden or lawn. Butterflies are attracted to the sweet, malty smell of beer and will transform your backyard into a butterfly haven in no time. Plus, plants love beer and will thrive from the sudsy drink.