How long does it take for alcohol to reach the brain?
About half a minute....
Once you swallow Alcohol (Ethanol, and preferably in an alcoholic drink of some sorts) it arrives in your stomach. As it is a standard, small metabolite it doesn't need digestion and passes the stomach lining, to be taken up in the bloodstream straight away.
The RATE at which this occurs varies for everybody and depends on a lot of physiological factors: amount of alcohol ingested at first swallow, nature of alcoholic drink, gender, condition of the stomach-lining, contents of the stomach (food), current blood-composition, presence of prescribed drugs, body weight, etc.
As the heart pumps our total volume of blood around in approx. 1 minute, it will take roughly about 30 seconds for the first molecules of alcohol to pass the Brain-Blood Barrier and affect the Neurons.
The satisfaction of that first sip isn't due to Alcohol, though: it has more to do with our built-in Reward System.
The effect of alcohol is negligible at first of course due to the low concentration, but with the passing of minutes it becomes more and more noticeable: In 2009 a research group from the University of Heidelberg reported a noticeable effect within 6 minutes:
The strength of the effect depends on the type of beverage:
This graph represents the alcohol concentration in Blood of course, but as stated, it reaches the brain straight away from there....