I agree with you that people who drink alcoholic beverages set a bad example, especially for young people. But, as a matter of fact, it is quite difficult to forbid it, unless these people drink too much. Once I had such a case and I decided to declare the game lost for the drunkard. Furthermore, I removed him from the playing venue and even brought him to his room. It is very difficult to give a general guideline, but, as long the drinking player is quiet and makes his moves in a normal manner, I do not see any reason to intervene.
Frankly, I don't mind players who take a glass or two to a game. Seems rather civilised, if you ask me. As long as they're not doing an Ukhov, I have no worries. Indeed, I recall playing against Paul Dozsa once (a fellow who, some of our local readers will remember, fancied himself as a gourmand but sans the financial commitment), while he drank a glass of red, taking a careful sip after every move. It was in the Fairfield RSL and the vino was $5 a glass.
What I do mind are players eating. That is just a no-no. Grubby, oily and sticky fingers make for grubby, oily and sticky pieces! Not to mention the sometimes deathly aroma of a triple heart bypass waiting to happen from a bowlful of chips. As far as I am concerned, eating ought to have no place at the chess table. Honestly, I should invoke that "distraction" rule the next time I see this across from me.