Green’s Dictionary of Slang

(Aus.) cheap or second-rate wine.

1930		(con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier 151: Plink-Plonk.—Facetious for vin blanc. A variant was plinkety-plonk.
1949		R. Park Poor Man’s Orange 107: Anything came well to the Kidger, plonk, plink, metho, bombo.
1972		B. Wannan Folklore of the Aus. Pub 128: Those who can’t afford plonk must be contented with plink—cheap plonk.
1980		(ref. to 1920s–30s) Hepworth & Hindle Boozing out in Melbourne Pubs 15: Affectionate nicknames for the stuff itself were: scarlet runner, [...] pinky, plonk and plink.
1999		Indep. Rev. 11 Nov. 7: In Australia plink [...] has been around as a term for such wine since the beginning of the century.