Ways to Keep from Falling Sleep. » The simplest way to stay completely alert and feel energetic throughout the day to is get 7 to 9 hours of sleep at night. But if you still have the tendency to fall asleep at odd hours of the day, then try the following tips. » If you are looking for the easiest way to stay alert during the afternoons, then drink a glass of cold water. It would simply refresh your body and mind by helping your body to get rid of toxins.