Green’s Dictionary of Slang

1. (US) illegally distilled liquor, based on various fruits and vegetables and usu. specified as such, e.g. tater jack (potatoes), prune jack, raisin jack.

1894		DN I 331: In Salem, Sussex, and Burlington counties [N.J.], where apple-whiskey is made, it is commonly called ‘jack’ [DA].
1935		J. Conroy World to Win 206: The bottle held strong but pleasant-tasting home-made prune-jack.
1946		Reader’s Digest Aug. 160/1: A New Year party for me and you with a side of beef and a gallon of jack to wash it down [DA].
1965		H. Rhodes Chosen Few (1966) 50: Blood had seen it before but hadn’t had any. Raisin jack. That semi-potent homemade concoction.
1982		G. Newbold Big Huey 127: All the queens and some of the boys had been drinking raisin jack.
1992		Bentley & Corbett Prison Sl. 70: Jack also Raisin Jack, Apple Jack [...] Prison-made wines.
2001		(con. 1975–6) E. Little Steel Toes 17: That’s where we cook our pruno, raisin jack, and my favorite, the beverage made from fermented tomato puree with fruit juice. [Ibid.] 18: Joe Moppa [...] maker of the finest tomato jack in da world.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 94/1: 3 = brew; homebrew.

2. (W.I.) illegally distilled rum.

1973

cited in Allsopp Dict. Carib. Eng. Usage (1996).

3. methylated spirits, used as a drink; thus jack man, one who habitually drinks meths.

1965		T. Cullen Autumn of Terror 28: The ‘meths’ or the ‘Jack drinkers’, as the derelicts who drink methylated spirits are called.
1996		R. Rendell Keys to the Street 59: The meths and water mixture, cloudy white fluid the jacks men called milk.