George Thompson, 36, also left his own passengers - an adult and three children - with serious injuries including fractured and broken bones.
The collision happened on the evening of September19, 2019 on the A6055 at Leeming Bar.
Thompson, of Sprotbrough near Doncaster, was driving a white Ford Transit van. Nobody in the vehicle was wearing a seatbelt.
He left McDonald’s at Leeming Bar, travelling north, and overtook a vehicle in front of him.
After the overtaking, Thompson failed to return to his side of the carriageway and continued driving on the wrong side of the road.
He hit a car which was driven by Richard Blain, a 37-year-old military serviceman who lived near Thirsk.
Mr Blain suffered extremely serious injuries and died at James Cook Hospital later that evening.
Thompson failed a police drugs test, which showed he had illegal levels of cannabis in his system.
During interviews, he initially tried to blame his victim for the collision. But he was charged with causing Mr Blain’s death by careless driving while being over the prescribed limit for illegal drugs. He pleaded guilty at court.
The case was heard through Teesside Crown Court, sitting at York Crown Court today.
As well as sentencing Thompson to three years six months in prison, a judge also banned him from driving for four years, nine months on his release and ordered he will have to take an extended retest.
Mr Blain’s family today described him as a devoted family man who will be deeply missed.
They said: “Richard was a wonderful daddy, a loving husband, treasured son and brother. His loss to his family, friends and colleagues will always be felt deeply and his memory will cherished dearly by all.”
Traffic Constable Gemma Brett of North Yorkshire Police’s Major Collision Investigation Unit, said after the sentencing: “This devastating collision has had horrendous consequences for so many innocent people.
“My deepest condolences go out to Mr Blain’s family, who have had their lives shattered by the staggering selfishness of George Thompson.
“Driving with illegal drugs in your system is one of the most dangerous things you can do on the road. Sadly, we see the consequences all too often – they are irreversible and they ruin lives.”