Green’s Dictionary of Slang

schmeck n.

1. (drugs) heroin.

1932		Eve. Sun (Baltimore) 9 Dec. 31/5: Smeck, dope.
1953		Anslinger & Tompkins Traffic In Narcotics 315: smack, smeck, schmeck. Drugs, especially powdered drugs in the form of snuff.
1958		A. King Mine Enemy Grows Older (1959) 44: We used to mix schmeck for Mike Malasino.
1965		H. Huncke in Huncke’s Journal (1998) 31: He called and said he’d like to get some schmeck.
1967		P. Thomas Down These Mean Streets (1970) 328: ‘Schmack?’ my face told him. His hand opened up and the five-cent bag was trembling there.
1970		L. Sanders Anderson Tapes 97: She’s got a record, and she’s hustling right now—shmeck, tail, abortion—the whole bit.
1980		S. McConville ‘Prison Language’ in Michaels & Ricks (1980) 526: Heroin [is] shmock.
1981		H. Gould Fort Apache, The Bronx 221: On top of the booze and the blow [...] even a one and one of this shmeck would put him away.
1981		D.E. Miller Bk of Jargon 338: schmeck: Heroin.
2001		ONDCP Street Terms 19: Shmeck/schmeek — Heroin.

2. cocaine.

1969		R.R. Lingeman Drugs from A to Z (1970) 223: schmack [...] (1) heroin or cocaine. (2) by extension, all drugs.
2001		ONDCP Street Terms 19: Schmeck — Cocaine.

In derivatives

schmecker (n.) (also shmecker, smecker)

(drugs) a heroin user.

1937		B. Dai Opium Addiction in Chicago.
1938		D. Maurer ‘Lang. of the Und. Narcotic Addict’ Pt 2 in Lang. Und. (1981) 109/1: smecker. A narcotic addict.
1953		‘William Lee’ Junkie (1966) 77: Don’t having anything to do with Sol. He’s a shmecker.
1969		R.R. Lingeman Drugs from A to Z (1970) 223: schmecker A heroin user.
1972		E. Grogan Ringolevio 44: O’Keefe went along, agreeing that the time seemed right for him to become a ‘shmecker’ too.
1981		D.E. Miller Bk of Jargon 344: schmecker: Heroin user or addict.

In compounds

schmeck biz (n.)

heroin dealing.

1959

J.E. Schmidt Narcotics Lingo and Lore 163: Schmeck biz – The illicit trade in narcotics. Schmecken – [...] addiction narcotics.