The natural sugar in fruit provides a quick pick-me-up when you're dragging and helps keep blood sugar levels steady because it's packed with fiber. Make an energizing breakfast smoothie with blueberries (helps you focus), strawberries (high in vitamin C, which helps turn fat to energy) and yogurt (rich in magnesium, which helps regulate the release of energy). Or toss in a tropical fruit like pineapple, which contains iodine to help control how quickly your body burns energy. Not a smoothie person? Fruits with peels, like bananas or apples, are good choices to take to work or when you're on the go.