It's unusual to drink beer for lunch and nothing else.
Tom does not have much money but agrees to go out with his coworkers to a local pub during lunch.
Tom wants to have fun with his friends.
Tom uses his money to buy one beer and some cheap food.
Tom uses all his money to buy two beers in order to keep up with his coworkers.
Tom is able to join his coworkers for a drink while not impairing or depriving himself.
Tom doesn't perform well at work later because he didn't eat anything and the alcohol had no buffer.