the cup. Put by Figure of speech Metonymy (of Subject), for its contents. See Jeremiah 25:15.
Related Commentaries of Jeremiah 49:12
Jeremiah 49:12
12 For thus saith the LORD; Behold, they whose judgment was not to drink of the cup have assuredly drunken; and art thou he that shall altogether go unpunished? thou shalt not go unpunished, but thou shalt surely drink of it.