The Golden Square man, now 20, was celebrating his 19th birthday in July last year when he assaulted a man through the window of a taxi at the Bridge Street cab rank.

The teenager had downed an entire bottle of spirits before going to a nightclub in Bendigo's central business district with friends, Bendigo Magistrates Court heard.

Shortly after 3am he and several friends left the nightclub and pushed into the taxi queue, jumping into the first vehicle in the rank.

The court heard when the man at the front of the queue leant down to the taxi's window, the teenager lashed out, punching him to the head up to six times, before fleeing the scene in the taxi.

He pleaded guilty to the assault on Wednesday.

Police prosecutor Senior Constable Karl Mannes told the court the intellectually impaired victim suffered injuries including a fractured eye socket and extensive swelling around his eye.

A victim impact statement prepared by the victim's mother and read to the court described the assault as "a senseless and unprovoked attack".

The court heard the victim had enjoyed going to nightclubs and was known to venue staff who looked after him.

Since the incident, he had become fearful of going out alone and worried he would come across his attacker or his friends.

Defence lawyer Luke Docherty said his client was sincerely remorseful for his actions and had written a letter of apology to the victim before being charged.

He said the teenager had left the nightclub after becoming unwell and was desperate to get home when he pushed into the taxi line.

Mr Docherty tendered three character references and told the court his client had never been in trouble with the law before, was gainfully employed and had good family support, giving him good prospects of rehabilitation.

"He can offer no reason or excuse for his behaviour,"  he said.

"He's otherwise and young man of good behaviour."

Magistrate Richard Wright said the offending deserved the strongest condemnation of the court.

"It was a vicious assault in the context of alcohol." Mr Wright said.

"It's a classic situation of young men with too much grog on board."

But he said the accused was a young man with his life in front of him, who would carry the incident with him for a long time.

Mr Wright sentenced him to a 12-month community corrections order, without conviction, and 150 hours of unpaid community work.

He also banned him from entering the Bendigo central business district between 10pm and 6am on Thursday, Friday and Saturday nights.