The green whistle is an inhaled analgaesic (pain relief). It resembles a vape, and contains a powerful drug known for making people extremely high. People who are "green-whistle'd" will often say inappropriate things, with their demeanor resembling that of a meth-head.
It is known internationally due to it's prevalence in the show Bondi Rescue.
"Hey mate, Damo's been green-whistle'd."
"Parramatta Eel" - Jethro (Bondi Lifeguard on the green whistle)
"Oi Leslie, you got a spare cigarette?" - Bondi Rescue Patient (who does not smoke) to Paramedic (not named Leslie)