DJing when drunk, let alone drinking, is foolish. I stay away from the bottle entirely. I don't want my brain cells killed and get b1tch tits from increased estrogen production. Besides from experience of watching those who have been drunk, girls take you less seriously. If you ask a girl's number, a lot of times they will say "Ask me when you are sober." This has happened before...many a time.
I like to DJ sober because everything flows better. No slurred speech, less chance of me saying something ridiculous, etc. In fact, I stay away from DJing in parties and in clubs anyway. I do my best in the most unlikely of spots (waiting in line for food at my college cafeteria, waiting for an elevator, and so on)