Green’s Dictionary of Slang

(Aus.) a wash; also as v.

1905		Duke Tritton’s Letter n.p.: I came to a Bullock’s Liver where I reckoned I’d have a Lemon Squash and liven up a bit.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxvi 4/1: lemon squash: A wash; a tub.
1968		J. Alard He who Shoots Last 137: To have a lemon, as they called it, was one of the big events of the day.
1969		S.T. Kendall Up the Frog 11: Up the apples and pears to lemon squash me Ramsgate Sands.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 35: Lemon Squash Wash.
2002		Pete’s Aussie Sl. Home Page 🌐 lemon squash: a wash.