Aim for a low-calorie snack that includes at least two different food groups, says Kristi King, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics. Spread 1 tablespoon of peanut butter on an apple or try a few whole-wheat crackers with one ounce of low-fat cheese.
Need some extra oomph? Consider pouring another cup of coffee (or tea) for a brain boost. If you don't want caffeine, chewing gum (particularly mint) can perk you up and wake up your brain. When researchers measured changes in pupil size as a sign of sleepiness, they found those who had been chewing gum were more alert compared with those who weren’t.