The 25-year-old man was allegedly caught sitting on a Toyota Corolla's window sill while speeding along Aikman Drive, with only his legs inside the car, at 4am Wednesday.

Police allege the man, who they say had also been going 10km/h over the speed limit, had told officers he did it because of a bet.

The man, who had an Indian driver's licence and was subject to a blood alcohol limit of zero, returned a breath test of 0.090 at Belconnen Police Station.

ACT Policing officer in charge of Gungahlin Station Inspector Rachel Hutka said no bet was worth risking your life and the lives of others.

"Drink driving is dangerous. Driving from anywhere other than the driver's seat is also dangerous," she said.

The man was served with an Immediate Suspension Notice, and is expected to appear in court on Monday August 10 to face charges of drink driving and negligent driving - other than death or injury.