Travelling at speeds of up to 144kmh, he fell asleep at the wheel and crashed into another lorry.
When he awoke, Andy Cheong Chin Chye, 30, found his friend of 15 years, Mr Tee Teck Eng, 29, dangling out the front windscreen.
Cheong's elder brother, who was driving in a car behind him, stopped and tried to help, calling the police.
But Cheong stole his brother's car and fled the scene.
Yesterday, he was jailed for 11 months and six weeks after pleading guilty to one count of causing death by dangerous driving, and two counts of failing to stop in the case of an accident.
Another charge of taking his brother's car without consent was taken into consideration.
Cheong will also be disqualified from driving for nine years upon his release.
At about 8pm on Dec 14, 2018, Cheong and Mr Tee had dinner and drinks at a coffee shop near Pioneer Road North.
Cheong had two cups of beer.
His elder brother also went to the coffee shop to pick someone up, and they all left together at about 10.50pm.
Mr Tee took a ride from Cheong, who offered to drive him home in his lorry.
At about 11.35pm, at a slight bend on the Ayer Rajah Expressway, Cheong's lorry swerved from lane 1 to lane 2, colliding with another lorry.
Both vehicles skidded left into guard railings and a traffic sign.
Mr Tee was thrown forward, crashing through the windscreen where he was left dangling when the vehicles stopped.
After seeing the state of his friend, Cheong took his brother's car and drove home, and returned to the scene only at about 3.30am the next day after numerous calls and much persuasion from family members.
He failed the breathalyser test there and was arrested.
But when he was taken back to the police station, he was unable to blow into the breathalyser for reasons not revealed in court, and they took his blood which turned up negative for alcohol.
Mr Tee was taken to hospital, but died from a head injury at about 5.30am.
Yesterday, Cheong admitted he felt sleepy prior to the accident and did not have proper rest, having started work at 9am and ended at 8pm that night.
Deputy Public Prosecutor Kevin Ho told the court that Cheong was previously convicted of similar charges in 2013, and should have known better than to leave the scene again.
District Judge Toh Han Li handed Cheong the sentence after considering all factors of the case, including his past conviction.
He also allowed a deferment of the sentence on the condition of increased bail.
For causing his friend's death by dangerous driving, Cheong, who is out on $15,000 bail, could have been jailed for up to five years.
He is expected to surrender himself on March 5 to begin serving his sentence.