Samuel Patterson inflicted a suspected broken nose on the other man after a fight broke out at the premises in the east of the city.
Sentencing the 37-year-old to four months behind bars, a judge told him people have been killed by such attacks.
Patterson, of Strathearn Park in Belfast, was convicted of assault occasioning actual bodily harm, disorderly behaviour and resisting police.
Police were called to Winemark on the Newtownards Road after a brawl broke out on August 6 this year.
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Belfast Magistrates’ Court heard officers found a man on the floor with his face and clothes covered in blood.
According to the prosecution Patterson had been present, behaving so aggressively towards staff that they activated the panic alarm and told him to leave.
As he approached the exit a fight broke out between him and the victim.
The other man threw punches, but was brought down and attacked on the floor.
He was kicked and punched repeatedly while on the ground before two members of the public pulled Patterson away.
“However, he returned to (the injured party) and appeared to stamp on his head on a further two occasions,” a Crown lawyer said.
“The injuries were a large cut to on the forehead and a suspected broken nose.”
Patterson was subsequently located and arrested at nearby Enid Parade, where he emerged from a house and started shouting and swearing at police.
Defence barrister Richard McConkey said the victim did not cooperate with the investigation.
“It’s not a case of somebody going into Winemark to buy a couple of beers and being set upon, it’s quite the opposite,” counsel submitted.
“Mr Patterson was attacked and he accepts his behaviour went well beyond what would be justified as self-defence or reasonable force.”
With the defendant already in custody for a separate case, District Judge Ted Magill told him he could have been facing a further eight months imprisonment.
“Kicking someone to the head, or stamping on someone’s head in particular, is incredibly serious,” Mr Magill said.
“I have seen people die as a result of such attacks, I have seen people rendered bound to a wheelchair for life as a result of such an attack.”
Imposing a total term of four months for the new offences, the judge confirmed: “It will be served consecutive to your present sentence.”