After the Great Britain Beer Festival in London, all the brewery presidents decided to go out for a beer. The guy from Corona sits down and says "Hey Senor, I would like the world's best beer, a Corona." The bartender dusts off a bottle from the shelf and gives it to him. The guy from Budweiser says "I'd like the best beer in the world, give me 'The King Of Beers', a Budweiser." The bartender gives him one. The guy from Coors says "I'd like the only beer made with Rocky Mountain spring water, give me a Coors." He gets it.
The guy from Guinness sits down and says "Give me a Coke." The bartender is a little taken aback, but gives him what he ordered.
The other brewery presidents look over at him and ask: "Why aren't you drinking a Guinness?" and the Guinness president replies "Well, if you guys aren't drinking beer, neither will I."