Jack Lloyd Kay, 20, of Gosmore, was driving a Peugeot when it overturned near Hitchin early on 4 October 2015.
Jack Mudd, 19, who planned to go to a US university to continue his golfing career, died in the crash.
Kay had already pleaded guilty to causing death by careless driving while over the alcohol limit and was sentenced at Cambridge Crown Court.
Mr Mudd's family spoke after his death of their "pure devastation", saying: "We simply cannot imagine life without you."
Kay was also banned from driving for two years and will have to take extended retest before driving again.
The friend of an aspiring young golfer killed in a car crash has been jailed for 18 months for causing his death.