Green’s Dictionary of Slang

cocoa.

1918		Bowen Indep. (Qld) 27 Apr. 3/2: Navy cocoa, which Princess Mary thought might be good to eat as chocolate, is known aboard ship as ‘ki’.
1935		Sydney Mail 31 July 10/2: Next item on the programme is early morning cocoa, for some obscure reason called ‘ki’. Sailors will assure you that its strength may be measured by the angle at which the spoon will stand in it without human aid.
1942		Northern Star (Lismore, NSW) 2 jan. 8/6: The Royal Navy, which first took to cocoa a century ago, absorbs 300 tons of it. [...] The cocoa, or ‘ki’ as they call it on the lower decks [etc].
1945		D. Bolster Roll On My Twelve 136: Time they pushed out the kye-boat.
1984		(con. WW2) T. Jones Heart of Oak [ebook] There I was to learn [...] cackleberries and kye, bangers and Spithead pheasant, underground pheasant and doctor’s chum, and keep my bobstay and shit-kickers clean [etc.].
2001		(ref. to 1950s) C. Lee Eight Bells & Top Masts 145: The sailor drank kai, a thick choclate brew made with spoonfuls of thick condensed milk.
1977		G. Melly Rum, Bum and Concertina (1978) 45: We also did a lot of skiving and sat for hours at a time drinking ki (naval cocoa).