I'm surprised "cronk" wasn't in the American Underworld Dictionary. That being the case, here is its definition:
Cronk n. 1. Slang word for liqour, particularly of the poorly-produced, highly alcoholic variety. Used primarily in 1930s detective novels and gangster movies. Syn: moonshine, rotgut, hooch. 2. Common slang for heroin in the low-income, inner city parts of large metropolitan areas. Syn: hehrawn, scag, crank, China white, Mexican brown.