*knock (something) back*
Definition: to drink an alcoholic drink very quickly.
(This phrasal verb has more than one meaning)
E.g.1: He realised that he was late, so he knocked back his drink and left the pub.
E.g.2: She gave me a glass of Tequila and told me to take a bite of lemon before knocking the drink back in one go.
This phrasal verb can be separated. (E.g. 2)