On hot days, no amount of water can replenish the electrolytes you lose when you sweat. But adequate blood levels of these minerals are key to energy since they help regulate the body's fluid balance. To rescue lost electrolytes, drink coconut water instead of reaching for flavored water. It is a natural mix of energizing electrolytes, including potassium and magnesium. One study proved that it's even more effective at rehydration than a popular sports drink.