umm i'm drunk so probably not my best answer but.... in small amounts alcohol acts like a stimulant. when your tipsy, buzzed, whatever you feel upbeat and happy. once your drunk alcohol acts like a depressant and your judgement is impared, your inhibitions way down, and your motor control is like gone. that is when you get sleepy. then again every body reacts slightly different. if i take cough syrup with codine (which sould make you sleepy) i am up for days. so really it all depends on you and how you personally react.
drinking a little, yeah, i can't sleep. drinking to the point of drunk knocks me flat. i literally pass out.