Paul Sandford, also known as Paul Dyson, was sleeping at his home near Rotherham when Adam Goodridge repeatedly punched him before taking photos of his injuries, police said.
The 38-year-old died in hospital five days later on 4 November 2015.
Goodridge, 31, of Huntington Way, Maltby, was found guilty of manslaughter at Sheffield Crown Court.
South Yorkshire Police said Goodridge, who denied the charge, had gone into Mr Sandford's house on Littlehey Close, Maltby, at about 01:00 GMT on 30 October.
He then attacked his victim in a "despicable" and unprovoked attack.
Goodridge had previously threatened to kill Mr Sandford "if he did not move from the area within a week".
Det Insp Simon Palmer said: "Goodridge then briefly left the room and even had the audacity to say that he would buy Mr Sandford's friends a beer, before returning to the room to continue his attack.
"He told Mr Sandford's friends to tell ambulance staff that he had fallen in the bath, but when emergency services arrived it was clear that his injuries has been caused by this unprovoked, cowardly and brutal attack."
Mr Sandford suffered a bleed on the brain, a fractured eye socket and severe cuts and bruising to his face and hands.
In a statement, his family said they had been "left a gaping hole in our hearts which is never going to heal" and described Mr Sandford as "a kind, caring and sensitive man".
The family said: "From the age of eight, Paul had suffered from ongoing health problems and the indescribable actions of Goodridge on that night have robbed us of the precious time we had left with him.
"We should be making lasting, happy memories with him right now, but instead we are left with the utter devastation of having our son, brother and friend taken away from us."
A man who killed a sleeping man in a "cowardly and brutal attack" has been jailed for 12 years.