5. Get some sun
An obscure lighted room is most likely to make you feel sleepier. As you feel drowsy go outside to bask in the warn sun beams. If there is no such opportunity at least stand by the window for some time. You might be surprised but sunlight provides our body with natural cues, which make us feel awake and alert. Moreover, being in the sunlight makes your body produce vitamin D, which is supposed to help fight tiredness.