Dominic Elliott, 23, died in March after he was taken to hospital from the world-renowned artist's house in Bridlington, East Yorkshire.
The inquest in Hull heard Mr Elliott had taken cocaine, ecstasy and temazepam before he drank the liquid.
Mr Hockney was in bed asleep at the time and was "completely unaware" of what had happened, the inquest heard.
The artist's former partner, John Fitzherbert, told the hearing he drove Mr Elliott to Scarborough Hospital in the early hours of the morning.
Mr Fitzherbert said that in the day leading up to the incident, he and Mr Elliott had drunk alcohol, taken cocaine and smoked cannabis.
Pathologist Dr Richard Shepherd told the court that temazepam and ecstasy were also found in his body.
Dr Shepherd said the acid severely burned Mr Elliott's mouth, tongue and throat before perforating his stomach.
Mr Hockney, who was not in court, said in a statement read out at the inquest that he had been asleep in his bedroom and woke up on the morning of 17 March to be told Mr Elliott had died.
The 76-year-old artist said he had gone to bed at 21:00 GMT the night before and despite seeing Mr Fitzherbert and his chief assistant, Jean Pierre Goncalves De Lima, at midnight there was "nothing out of the ordinary".
He did not see Mr Elliott before going to bed, Mr Hockney said.
He said Mr Elliott and Mr Fitzherbert had been in a relationship for about four months and described how a number of people lived in his five-bedroom former guesthouse, including Mr De Lima.
Mr Hockney said he had a large double bedroom where he also did portraits. He said Mr Fitzherbert had another large, self-contained room and they both led separate lives.
He said he had known Mr Elliott for about 10 years and described how he helped him with all aspects of his studio work.
But the artist said he only knew him "professionally" and he did not "really know him in a social aspect".
He said Mr Elliott sometimes drank a lot and this gave him a "Jekyll and Hyde" character.
"I cannot comment on any of the lifestyle habits he has," Mr Hockney said in his statement.
He said he had not been well at the time of the incident due to a mini-stroke.
Mr Fitzherbert, who was present in court, described how he and Mr Elliott had spent the Friday night drinking and smoking cannabis.
He said that on the Saturday morning, after Mr Hockney had left the house, Mr Elliott started laughing hysterically before jumping head first off a 9ft (3m) high internal balcony.
Asked by the coroner, Professor Paul Marks, why he did this, Mr Fitzherbert replied: "No idea".
He said Mr Elliott was not seriously hurt. "I just saw his feet going over," he told the court.
Mr Fitzherbert described how Mr Elliott later smoked more cannabis and they both fell asleep again together.
He said he was woken by Mr Elliott in the middle of the night asking to be taken to hospital.
Mr Fitzherbert told the court he found a bottle of toilet and drain cleaner in the sink but did not connect it to Mr Elliott at that time.
Pathologist Dr Shepherd had told the inquest that Mr Elliott would have been in extreme pain and Mr Fitzherbert was asked repeatedly whether he noticed this as he tended to his friend.
Mr Fitzherbert was also asked why he later called Mr De Lima to get him to tidy up the house.
He said Mr Hockney had not been well and he wanted to "shield him" from any "scandal involving drugs in his house".
Asked about why Mr Elliott did what he did, Mr Fitzherbert replied: "I do not have any answers."
"I think he liked living on the edge," he said.
Mr Elliott's mother, Karen Kent, told the inquest how her son met Mr Fitzherbert at a family barbeque when he was 15 years old.
It was Mr Fitzherbert who introduced him to Mr Hockney.
Mr Elliott's best friend, Christopher Towland, told the court he had recently become worried about his friend's gambling.
The inquest was adjourned until Friday.
David Hockney's assistant died after drinking acid at the painter's home, an inquest has heard.