A part-time Grab driver who drove under the influence of sleep-inducing drugs hit a cyclist without knowing he had done so.

Muhammad Fadzuli Mahmood, a technician by day, took on the driving job to earn more money.

On Oct 25, 2016, he took some cough syrup to induce sleep before he started his shift at midnight. He drove for a few hours before returning home as he was tired and sleepy.

At 5.30am, he went out again despite still feeling very tired and sleepy.

He took two epam tablets - which are actually used for insomnia - that he had bought in Lorong 12 Geylang to give him "energy to work for long hours".

Yesterday, District Judge Marvin Bay sentenced the 40-year-old to 15 months' jail and banned him from driving for eight years for causing the death of a foreign worker in Bartley Road East by committing a rash act.

Fadzuli also admitted to driving under the influence of drugs to such an extent as to be incapable of having proper control of the car.

Deputy Public Prosecutor Teo Lu Jia told the court earlier that Fadzuli was driving very unsteadily and swerving repeatedly along Hougang Avenue 3.

When he entered the slip road to Bartley Road East, he was still feeling drowsy, tired and sleepy. He kept driving in a very unsteady and dangerous manner, and did not notice Mr Karunanidhi Arul cycling along the road.

Because Fadzuli did not have proper control of his car, it veered to the right and mounted the kerb. He continued driving, side-swiping the rail guard in the process. He then collided with the 36-year-old construction worker without realising it.

It was only when he stopped to check the damage to his rental car that he saw Mr Karunanidhi lying unconscious on the grass. He called the police.

A toxicology report showed that Fadzuli had taken six kinds of drugs, including codeine and nitrazepam. His nitrazepam concentration was more than four times the toxic level.

All those drugs were found to have dangerous side effects such as sedation, sleepiness, disturbance in attention and reduced alertness.

In arguing for at least 15 months' jail and eight years' disqualification to be imposed for the charge of causing death, DPP Teo said Fadzuli's culpability was high.

She said the fact that he had deliberately taken drugs and chosen to drive in his intoxicated state was a serious aggravating factor which greatly exacerbated the gravity of the offence.

Just 10 days before the accident, he had paid a $200 composition fine for inconsiderate driving.

Fadzuli could have been jailed for up to five years and/or fined for causing death by a rash act.

For driving under the influence of drugs, he could have been fined up to $5,000 or jailed for up to six months.