The main plot might revolve around an encounter where a drink is involved. It could be that a character from one social background meets someone from another and the sharing or refusal of a drink sets off a series of events that explore their relationship and the broader social context.
Perhaps the story begins with a character being thirsty or in need of a drink. Then, through the process of obtaining or being offered a drink, they encounter various obstacles or revelations related to their identity and the society they live in. This could lead to a climax where the significance of the drink becomes clear, and then a resolution that may or may not resolve the underlying social issues.
It's possible that the drink in the passage is a central motif. For example, a character is invited to have a drink in a place where they are not usually welcome. This invitation could be a test or an attempt at friendship. As the story progresses, the character's decision regarding the drink and the consequences of that decision form the main plot, with the subtext being about the social norms and prejudices of the time.