Green’s Dictionary of Slang

1. a euph. for shit n. (1a)

1884		‘’Arry at a Political Pic-Nic’ in Punch 11 Oct. 180/1: Political Picnics mean sugar to them as is fly to wot’s wot.
1891		‘’Arry on a ’ouseboat’ in Punch 15 Aug. 76: And yet he will slate me like sugar, and give me cold beans with his charf.
1938		G. Kersh Night and the City 269: I respect a man who can gamble sugar or bust on a few throws.
1949		J.H. Burns Lucifer with a Book 63: But this longhair stuff is just shit and sugar to me, see?
1961		(con. 1945) G. Forbes Goodbye to Some (1963) 231: If the Aussies aren’t on Labuan . . . tough sugar for all of us.
1975		J. McClure Snake 30: ‘Oh, shhh-sugar,’ he said.
1985		J. Sullivan ‘Strained Relations’ Only Fools and Horses [TV script] Yeah, he’s as happy as a pig in sugar!
1989		J. Morton Lowspeak.
2015		Oxford American 1 July 🌐 Mitchell told Day that he was sure the record was a fiction. ‘I said, “Bullsugar,” ’Mitchell recalls [...] ‘Anyone that tells you they can beat the split screen is full of sugar.’ Mitchell tells me.

2. a contemptible person, a euph. for shit n. (2a)

1916

Joyce Portrait of the Artist as a Young Man 228: A flaming bloody sugar, that’s what he is!