Bulli man Christopher Machin, 20, yesterday admitted to grabbing the man's duffel bag and rummaging through it before pocketing a bottle of Swisse multivitamins.

Wollongong Local Court heard Machin and the victim were the only people on the station platform about 3.50am on September 10 last year, when an intoxicated Machin approached the man and began to harass him.

He then grabbed the man's bag and began to walk away.

When the man told him to give it back, Machin turned to face him, raised his fists and "took a fighting stance".

The victim, fearing he was about to be assaulted, jumped off the platform and ran across two sets of train tracks on to the other platform, where he called police.

Meantime, Machin rummaged through the duffel bag and took the vitamins.

Police arrived and arrested Machin.

Facing sentencing proceedings yesterday, Machin's lawyer, Gary Leo, said his client was a talented rugby player who had "poor impulse control" when he consumed alcohol. He asked the court to take into account Machin's early guilty plea and his co-operation with police, when handing down the sentence.

Mr Leo said the crime was not a planned one, noting it was all captured on CCTV cameras.

However, magistrate Darryl Pearce slammed Machin's behaviour. He said that people had a right to catch public transport "without being set upon".

"The facts appear to indicate there was no provocation on the part of the victim," he said.

"This robbery involved an innocent bystander who was in the wrong place at the wrong time."

Mr Pearce said he was satisfied Machin deserved a full-time prison sentence given the circumstances of the crime and other episodes of violence on his record.

He ordered Machin to spend a minimum of nine months behind bars, with a further three months to be served on parole.