Green’s Dictionary of Slang

to stink, to smell bad.

1912		Bulletin (Sydney) 31 Oct. 30/4: Twelve months ago it was a salt-encrusted plain of glistening mud, ‘ponking’ noisily with the festering remains of dead codfish and rotting lakeweed.
1941		Baker Popular Dict. Aus. Sl. 56: Ponk, [...] As verb, to stink.
1958		Willans & Searle Complete Molesworth (1985) 29: Some smoke cigs some smoke pipes poo gosh which ponk like anything. [Ibid.] 399: This place does not half ponk.