An initial inquest was told the three were declared dead at the scene of the crash.
The hearing was adjourned pending the outcome of further histology and toxicology tests.
Sophie Russon, 20, and Shane Loughlin, 32, were both injured but survived.
The accident happened near the St Mellons area of Cardiffon the A48(M).
A Volkswagon Tiguan veered off a slip road approaching a roundabout at 2.03am and came to rest in some trees.
The five were not discovered until Monday 6 March, around 46 hours after the crash took place.
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March: Vigil held for Cardiff car crash victims
The Independent Office for Police Conduct (IOPC) is continuing to investigate the length of time taken by Gwent Police and South WalesPolice to find the group.
Court papers seen by Sky News reveal the group had been drinking alcohol and inhaling nitrous oxide, commonly known as laughing gas, prior to the collision.
The group had been on a night out at The Muffler social club in Newport on the evening of 3 March, before travelling just under 40 miles (64km) to the Trecco Bay Caravan Park in Porthcawl.
They were last seen at about 2am in the Pentwyn area of Cardiff, where a sixth member of the group was dropped off.
The details emerged at the hearing of Joel Lia at Cardiff Magistrates’ Court, which was held behind closed doors.
Lia, 28, was the sixth member of the group who had been driving the vehicle an hour before the crash.
He was charged with driving without a licence or insurance in Porthcawl.
According to the court document: “All other persons in the vehicle were intoxicated, by Joel’s admission, as they had been drinking alcohol and inhaling nitrous oxide throughout the course of the evening.”
Lia’s case is being handled under a system called the single justice procedure where magistrates deal with non-custodial criminal prosecutions in private.
He pleaded guilty to both charges and the case was adjourned until 24 August.