Black and tans

From Theholdsteady

A type of beverage made from a pale ale and a heavier dark beer such as stout or porter. [1]. This is undoubtably the meaning explicitly meant by the character in the song. But do to the fact that the songwriter felt it necessary to clarify the meaning, "they mean the kind from the cans", it could implicitly be a reference to the Black and Tan regements used in Ireland to suppress revolution or uprisings amongst the Republicans. This varient would fit thematically with the earlier lines about the great white sharks, which act as a brutal, repressing force.