These popular products give you a jolt of caffeine, but too much caffeine not only can make you jittery, it interferes with normal sleep. Sleep deprivation shows up in puffy eyes and a cranky disposition. Furthermore, caffeine has been associated with encouraging fibrotic lumps in the breast. But the biggest downside to these uppers-in-a-can is the fact that most people who drink them do it at the expense of drinking water. Poor hydration is the skin’s worst enemy—setting the stage for wrinkles, fine lines, and dullness.