If someone is driving me to the airport (granted this may not be as effective if you live close to an airport) i will power nap in the car.
If im taking myself I will drink coffee to stay up through making it through the security check point and if i have time after ill grab another cup in the airport and some food if anything is open otherwise i half awake nap by the terminal and get sleep on the plane, and will get coffee when the snack cart comes by mid flight.
Or on some occasions if i don't have work the fay before an early flight i will take that day to last minute pack then sleep the day off so im ready to go in the wee hours of the morning.