Green’s Dictionary of Slang

(Aus.) a can or bottle of cold beer.

1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 33: What I need are a few swift coldies.
1972		G.W. Turner Eng. Lang. in Aus. and N.Z. 108: An Adelaide student reported [...] in 1968 that in April of that year her brother on a trip to Sydney found that the fashionable slang word was then crack. You would [...] crack a coldie ‘open a bottle of beer’.
1999		Indep. Traveller 27 Nov. 12: Five refer to beer: coldie, quickie, slab, stubbie and tinnie.
2009		P. Temple Truth 132: Buy you a coldie, then.