Real Simple tested 23 handhelds, looking for easy-to-empty dirt cups and machines that could efficiently pick up such everyday detritus as Cheerios, granulated sugar, lentils, pet hair, and coffee grounds. (We also tested the new wet-dry models but found that, for liquid spills, paper towels are the simpler solution.) The best finding? For a small investment, handheld vacuums are big time- and space-savers.