Green’s Dictionary of Slang

(UK prison) a form of punishment inflicted on sex offenders by other prisoners, involving scalding with hot water and sugar.

2004

N. ‘Razor’ Smith A Few Kind Words and a Loaded Gun 130: Put half a pound of sugar into a prison jug and top it up with boiling water [...] The sugar partly dissolves, so when the mixture is thrown in the victim’s face it clings to the skin and burns all the more. This activity is known as ‘jugging’.