John and Susan Cooper were on a Thomas Cook break at the Steigenberger Aqua Magic Hotel in the Red Sea resort of Hurghada, when they died on 21 August.
The pair, from Burnley, in Lancashire, were staying with their 12-year-old granddaughter, Molly, when they became aware of an “acetone type smell” in their room.
Later that night, Molly complained the smell was making her feel ill and Mr Cooper, 69, took her to the room where the couple’s daughter, and Molly’s mother, Kelly Ormerod was staying, with her other two children.
Senior coroner Dr James Adeley, who explained the chronology of events at the opening of the inquest, said: “They noticed an acetone type smell replaced by what is described by the granddaughter as a funny, musty smell.
“A different smell from earlier in the week. It was established the next door room had been fumigated.”
Ms Ormerod, 40, became concerned when she hadn’t seen the couple, who were not known to have any serious medical conditions, by 11am the following morning.
Mrs Cooper, 63, usually woke up by 6.30am to reserve sunbeds and then have breakfast.
The inquest at Preston Coroner’s Court heard Ms Ormerod called doctors when her father answered the door to the couple’s room, where he later collapsed.
He and his wife had been feeling lethargic, and had found to have been vomiting. The couple had both eaten liver at the hotel buffet, on 20 August.
Dr Adeley said: “Mr Cooper collapsed in the room and could not be revived and verified to have died at noon. Mrs Cooper was variably lucid.”
Mrs Cooper later suffered a heart attack in an ambulance on the way to hospital, where her death was confirmed.
Outside court Ms Ormerod asked for time to grieve the loss of her parents. Their funeral will be held in Burnley on Wednesday.
She said: “All I would like to say is thank you very much for all the support I have received.
“If you would kindly leave me be, leave my family be, and let us grieve and get the grieving process on the way, and I am prepared to speak at a later date.”
The coroner said that as the deaths happened outside the UK, he was able to only make information “requests” from the Egyptian authorities.
He added that post-mortem tests conducted in Egypt found their deaths were linked to E.coli bacteria, a finding their daughter earlier dismissed.
Egyptian authorities claimed the strange smell in the couple’s room was a leak of pesticides from an adjacent room that had been fumigated.
Post-mortem examinations on the couple in the UK have been inconclusive, and further tests are being carried out.
Dr Adeley said he would be asking the Egyptian authorities and Thomas Cook to hand over relevant documents, including forensic and toxicology reports, tests results on food and water, and details of the police investigation.