Brenton Healey's final disgusting acts against a 15-year-old girl included giving her painkillers that caused her to vomit and wet her pants before taking her virginity in a car.

At 32, he was more than twice her age.

His actions were patently predatory and disgraceful, Victorian County Court Judge John Smallwood said.

Healey was jailed on Friday for nine-and-a-half years and must serve six years and three months before he has any shot at parole.

He had initially become friends with a 17-year-old girl in April last year and later became friends with the younger girl.

Healey admitted charges of grooming a child for sexual offending, sexual penetration of a child, sexual assault of a child, involving children in the production of child abuse material and supplying drugs to a child.

In May last year Healey drove the girls to a park to "smoke crack", introducing them to ice. He later taught them how to snort lines of cocaine.

The girls said Healey asked for things in exchange for the drugs. Both were sexually assaulted by him.

"You exploited them for your own sexual pleasure," Judge Smallwood said.

He sent the younger girl explicit grooming messages, sent her photos of himself and received photos and videos in exchange.

Things escalated until the car incident, which the judge described as "almost incomprehensible".

"What you did to each of those children is disgraceful," he said.

"I can only hope you understand the devastating effect it's had on those two girls."

The girls removed Healey from their social media accounts the following day.

Later they went to his home, punching and kicking him. His mother called the police and the girls were arrested, prompting them to disclose what he had done to them.

When interviewed Healey admitted some of what he'd done but initially denied other parts.

He told officers the offending had started on a whim but he had gone too far.

Healey, now 34, will be registered as a sex offender for life.

Australian Associated Press