A court heard Jason Callendar attacked the guest after spending the day drinking at the event at Weetwood Hall Hotel, Leeds, on July 31 last year.
Duncan Ritchie, prosecuting, told Leeds Crown Court that the attack happened after police had been called to the wedding reception earlier in the evening as some guests had been abusive to hotel staff.
Callendar, 32, carried out the attack after sitting beside the victim as he was talking to another guest at a table.
Mr Ritchie said Callendar suddenly picked up a glass and struck the him behind the ear and to the back of the head.
The other guest tried to intervene and the three three men ended up struggling on the floor.
The prosecutor said: “The defendant was growling and bearing his teeth.”
Other guests managed to stop the attack and police were called.
The victim suffered a cut behind his ear and was bleeding heavily from a leg wound.
Callendar was arrested and found in possession of a small amount of cocaine.
He was interviewed about the incident the next day and initially claimed he had been acting in self defence.
Callendar, of Tong Approach, Wortley, pleaded guilty to assault occasioning actual bodily harm and possession of cocaine.
The court he has previous convictions for drink-related offences.
Michael Miller, mitigating, said Callendar was sorry for what he had done and had not been in trouble since the incident.
He said: “When the defendant drinks, he drinks to excess and that gets him in to trouble.
Callendar was given a ten month prison sentence, suspended for two years. He was also ordered to do 200 hours unpaid work and pay £500 compensation to the victim.
Judge Geoffrey Marson, QC, said: “You were under the influence of alcohol and cocaine and other people had to witness what you did.”