Why do Black Organization members use alcoholic drink names as code names?
There is a reason behind this.
Gosho Aoyama stated that there is a reason behind all the names of the, as we call it, Black Organization. He also said, that if we would knew the real name of the Organization, we would know the boss.

Now, we just have to wait until Mr. Aoyama reveals the real name. And it better be something better than "Bar", "Club" or "Organization of Alcoholic Drinks".