The victim then spent four more months in hospital and still suffers from long-term side effects, including memory issues, after the assault in mid-2013.

In the ACT Supreme Court on Tuesday, Saed Harmouche, 25, was sentenced to weekend detention for the attack.

The court heard Harmouche, of Oxley, had been on the crowded dance floor of Meche nightclub in July 2013 when he launched the unprovoked attack on the smaller man.

Harmouche punched the man in the head once, causing the victim to fall backwards and hit his head on the edge of the stage.

In August, Justice John Burns acquitted Harmouche on a charge of recklessly inflicting grievous bodily harm.

But Harmouche pleaded guilty to a lesser serious charge of, by an unlawful or negligent act, he caused grievous bodily harm.

A victim impact statement, tendered in court, said the man suffered from memory issues and had been forced to abandon his studies as a result of his injuries.

A medical report said he had suffered mild cognitive impairment, poor concentration, personality changes, and had become socially withdrawn.

He has since returned to Saudi Arabia where his mother had to quit her job to care for him.

Justice Burns, in handing down the sentence on Tuesday, said the injuries had been in the upper range for the type of offence.

The court heard Harmouche had missed a number of court-ordered appointments with Corrective Services staff and was arrested in September for not appearing at a sentence hearing.

A pre-sentence report said the offender had shown the victim empathy and taken responsibility for his actions.

He was rated a low-risk of general reoffending, but the report's author recommended he complete anger management and alcohol counselling courses.

Justice Burns accepted Harmouche had shown remorse for his offence and showed good prospects of rehabilitation.

The judge sentenced him to 15 months' jail, to be served as six months' weekend detention, with the remainder suspended.

Harmouche was also ordered to sign a two-year good behaviour order.

Justice Burns warned Harmouche to expect to spend time behind bars if he breached or did not comply with the court's orders.