Green’s Dictionary of Slang

1. (S.Afr.) to gulp, to swallow down.

1970		informant in DSAE (1996).
1972		A. Scoby on Radio S. Afr. 23 May [radio broadcast] Here — have a drink. Hey, hey, don’t sluk the lot! [DSAE].
1985		T. Baron in Frontline Feb. 30: ‘Cheers. Down the hatch.’ We slukked down a few [DSAE].

2. (S.Afr. Und.) to betray.

2005

A. Lovejoy Acid Alex 166: The only golden and much broken rule is never to sluk a brother. [Ibid.] They rob, thieve, connive, scale, sluk, skebeng and schnaai their way into anything.