In his findings, Coroner McElrea found they told a friend they were "going back to Tui's to pick up some shots", but there was no evidence to confirm the men had done so.
Sometime before 2am on May 11, the car was travelling along Hinds Arundel Rd in Ashburton at an estimated speed of 185km/h.
The car hit the side of a culvert, which police described as a launching ramp, which vaulted the vehicle skyward, Coroner McElrea found.
The car hit a power pole at such force the vehicle split in two. Both men were killed instantly.
Serious crash investigator Senior Constable McIntyre told Coroner McElrea the vehicle's speed was "close to just over 50m per second".
"So that's a football field every two seconds."
A toxicology analysis found Mr Ballantyne had a blood alcohol level of 156mg of alcohol per 100ml of blood. As he was under 20, his blood alcohol limit was nil.
In comments directed to the New Zealand Rugby Union, Coroner McElrea said the deaths of both young men were avoidable. He described the deaths as an example of "the mixture of sport and alcohol".
"The evidence is that the rugby team would regularly adjourn to the local tavern after rugby practice and drink alcohol."
Coroner McElrea said police had emphasised the importance of always having a sober driver.
"That is a message which may be self-evident, but needs to be said time and time again unfortunately.
"It is a message that needs to be taken on board, if has not already been taken on board, not only in the liquor industry but in the team culture; in this case, the rugby team."
The finding comes a day after the Ministerial Forum on Alcohol Advertising and Sponsorship made a series of recommendations, including a long-term goal of completely banning alcohol sponsorship in sport.
The forum, established by the Government in February, also recommended a ban on the advertising of beer, wine and spirits in relation to sports -- at stadiums, on television, in bus stops and other places likely to be seen by young people.
The proposals were based on findings linking young people's exposure to alcohol promotions with increased consumption and younger drinking ages.