Green’s Dictionary of Slang

sink n.

1. a drunkard.

[UK]Farmer & Henley Sl. and Its Analogues.
[Aus]Bulletin (Sydney) 11 Aug. 14/1: You were such a noble doer, such a persevering sink – / Fancy you to be a quitter when the world is full of drink.
[UK]Partridge DSUE (1984) 1072/2: mid-C.19–20.

2. (UK Und.) a supposedly legitimate business that used to facilitate money-laundering.

[UK]J.J. Connolly Viva La Madness 32: What you need is a ‘sink’, meaning quite literally somewhere you can sink your schwarzgeld into the system.

In compounds

sink-hole (n.)

the vagina .

[UK]‘The Sink-Hole’ in New Cockalorum Songster in Spedding & Watt (eds) II 11: He opened her dirty sink-hole wide, / And scraped the bottom as well as each side; / And when he had rummaged each corner about, / With his tools in his hand he quite tired crep [sic] out.