A champion swimmer and her boyfriend died in their metal-walled barn conversion when an electrical extension reel overheated, an inquest heard.
Tazmin Pugh, 18, and Josh Kirk, 21, choked on the fumes as the flames engulfed their home as they slept next to each other.
She won silver representing Great Britain at the Commonwealth Youth Games in Samoa in 2015 while Josh was heavily into music and carpentry.
The couple had returned to their home in Cotheridge, Worcs., from a party where they had taken a cocktail of recreational drugs before falling asleep.
A coiled electrical cable reel overheated which started a fire in the property in the early evening of October 28 last year.
An inquest heard the wood chips in the walls caused the inferno to rapidly spread and within minutes the couple were overcome by the deadly fumes.
Metal sheeting in the walls also meant there was a lack of ventilation which created a deadly oven effect in the barn.
Worcestershire Coroner David Reid said the couple had used recreational drugs "which may well have affected their ability to react to the fire".
Mr Reid told the inquest on Monday (23/9): "Both of them were young people full of promise.
"Joshua had done an engineering apprenticeship and had begun working again.
"Tazmin had been an elite swimmer winning championships and medals at the Commonwealth Youth Games."
The inquest heard that following an injury in 2017 Tazmin began to lose interest in her swimming career.
At around the same time she met Josh and they began a relationship and moved into a converted barn at his parents' home at the end of 2017.
Mr Reid said: "Both of them got involved in a lifestyle that involved weekend parties and recreational drugs.
"I want to make clear that I have not mentioned the couple's drug use to pass judgement on them, but it is relevant to what happened."
On the night of the fatal blaze, the couple had been to a party in the afternoon and had returned to the barn.
The couple had taken Phenazepam - a Russian equivalent to M-Cat - along with Amphetamine and Ketamine, most likely the day before the fire.
They had fallen asleep on the bed and a neighbour noticed the barn on fire at 8pm and dialled 999.
Mr Reid said: "The fire was well developed at this stage.
"It is likely that Tazmin and Josh had died well before the fire had reached that stage."
Recording a verdict of accidental death, Mr Reid said: "Most significant was the amount of carboxyhemoglobin.
"Carboxyhemoglobin is found in the body when carbon monoxide is breathed in.
"The development of the fire was increased by the significant amount of metal sheeting in the walls.
"The cause of death given in this case is one, the affects of the fire and two, mixed drug induction."
Mr Reid offer his condolences to the families of the victims for their "terrible loss."