Green’s Dictionary of Slang

1. (orig. US black) an attractive black individual, usu. a woman.

1926		Maines & Grant Wise-crack Dict. 6/1: Brown sugar – sweet but unrefined.
1937		C. Himes ‘A Nigger’ in Coll. Stories (1990) 30: Think of me, your little brown sugar, darling.
1949		Monteleone Criminal Sl. (rev. edn).
1961		C. Himes Pinktoes (1989) 102: Brown Sugar [...] was a big, handsome, [...] smooth, brown, luscious piece.
1971		Jagger & Richard ‘Brown Sugar’ 🎵 Brown Sugar, how come you dance so good?
1983		I.L. Allen Lang. of Ethnic Conflict 46: Color Allusions, Other than ‘Black’ and ‘Negro’: brown-sugar [fem. Also sugar-brown].
1987		personal ad. Murray & Murrell Lang. Sadomasochism (1989) 45: Look for brown sugar to play S/M games with, nothing too severe.
1993		J. Mowry Six Out Seven (1994) 93: Times I hear some of the truckers talkin bout that. Black ones be called brown sugar.

2. (drugs) heroin.

1977		N.Y. Times Mag. 9 Jan. 16: The Asian heroin is coarser—hence its nickname ‘brown sugar’.
1981		D.E. Miller Bk of Jargon 325: Also H, big H, blanks, boy, brother, brown, brown sugar, caballo.
2001		ONDCP Street Terms 4: Brown sugar — Heroin.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 31/2: brown sugar n. heroin.
2009		DNA India (Mumbai) 10 June 3/2: Drugs like opium, brown sugar [...] and a few synthetic drugs are smuggled by train .

3. lowgrade or adulterated heroin.

1977

L. Young et al. Recreational Drugs.

4. sexual intercourse with a black person.

1980		E. Folb Runnin’ Down Some Lines 150: Women, too, relate sex to the sweet-tasting with terms like to [...] get some brown sugar, for sexual intercourse.
1998		(con. 1986) G. Pelecanos Sweet Forever 4: Had me a little brown sugar action this morning.
2002		‘Touré’ Portable Promised Land (ms.) 160: We Words (My Favorite Things) [...] Jungle fever. Brown sugar.