Freeze your butt off. End your shower with a two-minute blast of cold water. Beyond eliciting a few choice swear words, cooler temps can wake up a sluggish mind, research shows Ifa full-body brrr is too much to handle, start by splashing frigid H20 on just your face. Get the giggles. Grab tickets to the new Zach Galifianakis comedy, Keeping Up with the Joneses Agood laugh will boost your blood flow within about 15 minutes. Ta-ta, brainfog. Swap caffeine for carbs. For sustained energy, you need grub, not another cup ofjoe. "Only calories give real energy," says nutritionist Keri Glassman, R.D. "You need carbs and fiber to control blood sugar, plus protein and healthy fat to keep you full." Try a baked sweet potato with a tablespoon of chopped nuts, or a slice of Ezekiel toast with avocado.