Footage has been released of the moment a driver leans out of his window to take a can of beer from a minibus on the M6 motorway in Staffordshire.
Paul Holmes, who's 24 and from Clitheroe in Lancashire, admitted dangerous driving and has been banned from driving for 15 months.
North Staffordshire Justice Centre heard he did it in "momentary stupidity" and gave the drink to his friend in the passenger seat.
Holmes can be seen in the dashcam footage travelling at 70mph on the motorway, driving right up behind another motorist to grab the drink from a passenger in the back of the minibus, which contained a stag party.
The court heard the motorway at the time was busy, and the civil engineer's actions could have had "catastrophic" consequences. Holmes's solicitor said he had been caught up in a "very exciting day".
Debbie Leadbeater, defending Holmes, said: "He had been to see his children in Birmingham. He picked a friend up and they were going to go out in the evening. They were passing this group of people who started to gesticulate and wave to them."
"There was banter with them, they were in high spirits. Momentarily he got caught up in the fervour of the stag party and bizarrely he agreed to take this can and give it to his friend."
"Throughout this time he had full control of the vehicle and did not look away from the road. He just put his hand out. It was momentary stupidity."
Mark Olszewski, chairperson of the bench, told Holmes: "What we saw on the footage has given us a great deal of concern. The potential outcome of that behaviour could have been catastrophic. It could have cost lives.
Holmes must also pay £280 in court costs and charges.