Sharing a dank condo with fellow dirtbags? Carry a packet of Emergen-C everywhere you go. Tear 'er open. Fill with water. Wait while the concoction becomes a fizzy syrup of electrolytes, 1,000 milligrams of vitamin C, and B vitamins. Then slam directly out of the packaging like a shot of Gu. -S.G. ($15 for 36 packets; emergenc.com)