"Excuse me. Can I speak to the driver? I need to speak to him," the woman allegedly said.
The plain-clothed Detective asked why, and she allegedly replied: "we're buying cocaine".
It is alleged she had messages on her phone, organising the drug deal.
Police will allege the driver then began "fanatically disposing plastic packaging down the side of his seat".
Police searched the car and allegedly found eight bags of cocaine and $3100 in cash.
The Guildford man was charged with disobeying a one-way sign, dealing with the proceeds of crime, supplying a prohibited drug and driving a motor vehicle while disqualified.
He will front Waverley Local Court next month.