Green’s Dictionary of Slang

1. (orig. US) a union-employer contract that favours the company over its employees; a union-employer contract that favours all those negotiating, but not the workers the union supposedly represents; thus sweetheart situation; sweetheart operator, one who negotiates such a contract .

1948		Jurisdictional Disputes in the Motion-picture Industry US Congress 2-3 2439: Now, if we . made a ‘sweetheart’ deal or a company union deal with the distributors, we made a bum one. We should have made them give them all to us and not just part of them.
1958		Life 21 July 16: Restaurant owners testified that picket lines were thrown up around their establishments. then removed only after they signed a ‘sweetheart’ contract with a union.
1964		Life 15 May 49: Any way you look at it, Hoffa was trying to sell us down the river, into a ‘sweetheart’ contract.
1965		Wall Street Journal (Eastern edn) 23 Sept. 1/6: The mine manager is a ‘sweetheart’ operator... In the classic ‘sweetheart’ situation, corrupt union leaders accept or extort payoffs from employers in exchange for assuring labour peace or winking at contract violations [OED].
1976		Backpacker Oct. 12: We taxpayers are getting ripped off by MCA, Inc.’s ‘sweetheart contract’ with the National Park Service.
1987		M.R. Wolfe Kingsport, TN 133: Some charged that a ‘sweetheart contract’ existed between Colonel Palmer and George Berry, a Hawkins County native and longtime president of the International Printing Pressmen and Assistants' Union.
1999		Gustafson & Jubiler Religion & Human Rights 86: The company formed a ‘dummy’ union and produced a ‘sweetheart’ contract.
2000		Simon Hoggart in Guardian 8 Mar. 🌐 That said, if just a quarter of what he describes is true, then the EU is wasting our money at an unimaginable rate. The cronyism, the blackmail, the sweetheart contracts, the manner in which several commissioners ran their departments as gravy trains for their friends and compatriots.
2008		Simon & Burns ‘More with Less’ Wire ser. 5 ep. 1 [TV script] It’s a sweetheart deal for a titty-bar owner with a big criminal history.
2017		D. Winslow The Force [ebook] Gerard Berger cut his client the sweetheart deal of all time. In exchange for providing intelligence on the cartel [...] Pena received two years minus time served.

2. in extended uses of sense 1.

2006

B. Matthews Intractable [ebook] I suffered the consequences of exposing the sweetheart deals between informers and New South Wales police officers.