My body can keep me awake via naturally produced chemicals if need be (such as adrenaline and dopamine). I do not train my body to rely on an introduced stimulant of any kind.
Proper nutrition, exercise, skills practice to increase efficiency, perceptual and mental acuity training, activity compatibilty management and time management, rest at appropriate times, and good attitude, are for the most part, all that is needed.
You don't need a pill. You are a dynamic being with inherent systems and subsystems galore.
Don't believe the hype about stimulants. They act disharmoniously in the human body. There are addictive. But, I think that if I was addicted to caffeine already, I would only drink small amounts of white tea, which has less caffeine than green or black.
Aside, tea also has flourine in it, and the general consensus concerning it is "No".