VIOLENCE flared up when a drunk and drug befuddled guest was found in bed with his girlfriend's sister.
Anthony Lee Newton, 25, got into bed with Whitney Collins by mistake, Barnsley Magistrates' Court was told.
His girlfriend, Shelby Caulfield, found them and hit Newton.
Philip Howard, defending, said Newton was forced out of the house and Ms Caulfield was in the back of a taxi.
There was a further argument and Newton punched her on the nose.
Jayne Ormrod, prosecuting, said there was blood everywhere after the attack in the taxi.
District Judge John Foster accused Newton of 'thuggish behaviour' and told him to get help with his drinking.
He said: "You need to do something about your drinking now. You were on the lash and taking drugs. Your girlfriend had a reason to be angry with you but you couldn't see that."
Newton, of South Road, Dodworth, was given a 16-week jail sentence, suspended for a year, and ordered to undergo six months of alcohol treatment.
Unusually, Mr Foster asked Ms Caulfield, who was sitting at the back of the court, how much compensation she wanted Newton to pay her.
Ms Caulfield said she didn't want a penny as she had forgiven Newton.
Newton, who admitted assault, was also ordered to do 80 hours of unpaid work, to pay £250 in costs and an £80 victim surcharge.