You could use stimulants. Coffee, nicotine (there is gum, but it is easy to be addicted and detoxing causes noticeable brain lag for a few days), and you could use nootropic stuff like adrafinil (works well for me).
Or the problem could be stimultants and the coffein lows after the spikes that causes the drowsiness. Try living without coffee for 2-3 weeks and see if it flattens your mood.