Or juice. Or decaffeinated diet soda. Drink anything but coffee, hot chocolate or tea within six to 10 hours of bed. Caffeine blocks the effects of adenosine, a chemical produced by your brain that makes you sleepy. In fact, studies have shown that the caffeine in even one cup will rev your circuits enough to reduce both the length and restorative depths of sleep. It will also wake you during the night to urinate.