After two weeks his life support was switched off. He died on November 5, 2015.
An inquest into the cause of his death found Mr Sandberg suffered a traumatic brain injury in the crash.
But the actions that led Mr Sandberg to lose control of his vehicle remain uncertain.
Coroner Carla na Nagara, who conducted the inquest, said the SCU investigator calculated the vehicle's speed to be below the speed limit.
"There was a half-eaten pizza in the car that suggested Mr Sandberg may have been eating or reaching for pizza and was momentarily distracted from his driving.
"This cannot be known with any certainty. There is no other evidence that can offer a possible explanation for the cause of the crash that ultimately claimed Mr Sandberg's life," Ms Nagara said.
Mr Sandberg had only been in the country for eight days prior to the crash.
He lived in Germany and worked as a vehicle transporter for BMW. He had travelled to New Zealand with the intention of touring the country.
His mother, Sylvia Sandberg, said her son was a good driver who did not drink or smoke.
Ms Sandberg travelled to New Zealand with her partner to be with her son after the crash.
Due to the seriousness of his injuries and his poor prognosis, the decision to withdraw life support was made.
Ms Nagara said medical investigations during Mr Sandberg's hospitalisation confirmed that he had suffered a traumatic brain injury, and that his injuries were unsurvivable.
"I accept the medical evidence that the cause of Mr Sandberg's death was a traumatic brain injury."