Green’s Dictionary of Slang

(Aus.) diarrhoea; thus have the cocktails.

1941		Baker Popular Dict. Aus. Sl.
c.1943		S .J. Baker Aus. Vulgarisms [t/s] 8: cocktails, have the: To be suffering from a bout of diarrhoea.
1955		N. Pulliam I Travelled a Lonely Land (1957) 233/1: flying handicap (the cocktails) diarrhoea.