Bhavesh Patel, 39, appeared to have his hands behind his head when he was filmed by a passenger in another car.
While driving his white Tesla S 60 along the M1, Patel switched on the supercar's autopilot function before moving to the passenger seat, leaving the steering wheel and foot controls unmanned, police said.
A witness, who spotted the vehicle with no-one in the driving seat, said they thought the car was going at around 40mph.
Patel, from Nottingham, pleaded guilty to dangerous driving over the incident on the motorway near Hemel Hempstead, in Hertfordshire, at around 7.40pm on May 21 last year.
At St Albans Crown Court on Friday April 20, he was banned from driving for 18 months, ordered to carry out 100 hours of unpaid work and 10 days' rehabilitation, and told to pay Â£1,800 costs, police said.
Patel told officers he knew what he had done was "silly", but said the car was capable of something "amazing" and that he was "the unlucky one who got caught".
Pc Kirk Caldicutt, from the Bedfordshire, Cambridgeshire and Hertfordshire road policing unit, said: "What Patel did was grossly irresponsible and could have easily ended in tragedy.
"He not only endangered his own life but the lives of other innocent people using the motorway on that day.
"This case should serve as an example to all drivers who have access to autopilot controls and have thought about attempting something similar.
"I want to stress that they are in no way a substitute for a competent motorist in the driving seat who can react appropriately to the road ahead.
"I hope Patel uses his disqualification period to reflect on why he chose to make such a reckless decision on that day."
Investigators were told by a Tesla engineer the autopilot function, including traffic-aware cruise control and auto-steer, is intended to provide assistance to a "fully attentive driver".