Green’s Dictionary of Slang

drink n.4

1. a bribe, a sum of money that would supposedly purchase ‘a drink’ but is usu. much larger.

[UK] ‘Metropolitan Police Sl.’ in P. Laurie Scotland Yard (1972) 322: drink, a: a bribe.
[UK]D. Powis Signs of Crime 181: Drink Euphemism for blackmail payment or a money bribe. ‘There’s a drink in it for you’ may mean there will be such payments.
[Aus]R.G. Barrett Real Thing 11: He slid the two fat envelopes across the desk. ‘There’s a nice drink there and there’ll be another one [...] when all this is settled.’.
[UK]J. Morton Lowspeak 52: Drink [...] Probably up to about £25, as opposed to a big drink which starts in the hundreds.
[UK] in D. Campbell That Was Business, This Is Personal 19: I want a drink out of it [i.e. a robbery] but I’m not in on it.
[UK]K. Sampson Outlaws (ms.) 133: He does get a good drink for his services, to be fair. He’ll get thirty large out of this.
[UK]J. Cameron Hell on Hoe Street 114: ‘Bung you a fuckin’ drink you meaning?’ ‘I am liking Swiss francs very much.’.
[SA]‘A-Z of South African lingo’ in IOL News (Western Cape) 3 June. [Internet] C for Cooldrink: A chilled soda or a euphenism for a bribe. eg ‘If you buy me cooldrink, I’ll forget about that speeding fine.’.
[UK]K. Sampson Killing Pool 66: We give him a drink and he’ll carve the bread however we want.

2. a tip, a commission, a bonus.

[UK] in G. Tremlett Little Legs 115: Charlie [...] might just take a drink out of it.
[UK]Guardian Sport 12 Feb. 16: Give Marco a ring, could be a nice little drink in it.
[UK]J.J. Connolly Viva La Madness 366: Oh, and Curtis wanted a drink outta it.