Con Arvanitis was sentenced to seven years and 10 months jail after pleading guilty to charges of sexual penetration and supplying drugs of dependence to a child.

The court was told the child had mentioned she first met Arvanitis through the app MeetMe, which uses the user's location to match them with strangers.

She described it to police as being "like Skout", another location-based social app, but "it's like a dating app but it's mainly selled off drugs and you don't really know who anyone is".

The child, who was in the care of the Department of Families, Fairness, and Housing at the time and was described as highly vulnerable, gave her Snapchat username to Arvanitis, who began messaging her.

She told him she was 14 at the time repeatedly but he continued to message her, eventually inviting her to his house in Footscray to smoke meth in June 2022.

Arvanitis was initially charged with supplying drugs to a separate child, aged 17, and jailed for 40 days, released on a strict community corrections order in the days before inviting the child to a second meeting.

Judge Marcus Dempsey said Arvanitis then "breached that CCO in the most egregious and aggravating way within a fortnight".

Arvanitis continued to message the child through Snapchat, eventually inviting her back to his Footscray home, and supplying more meth to her, including through a needle.

He then sexually assaulted her over 40 minutes, in acts that were described as "at times brutal, degrading and bordering at times on malevolent".

The child eventually left and told her case manager, who informed police, and Arvanitis was arrested the next day.

Police found "a significant number of messages using the application 'MeetMe' where (Arvanitis) had made contact with various persons offering 'puff' sessions".

Arvanitis' lawyer stated there were significant psychological problems, including drug abuse, anxiety and depression.

"Your moral culpability is heightened given that you preyed upon a vulnerable victim compromised by the effect of a drug. Her vulnerability arises because she was, of course, a child, and what is more, substance affected - factors which you were well cognisant of," Judge Dempsey said.

"Remorse is a vexed issue here. Your initial denials to police suggest that you were prepared to lie rather than admit your conduct and display contrition for it."

Arvanitis was jailed for seven years and 10 months, with a minimum four years and nine months before being eligible for parole.

Affected by this story? There is help available.

You can phone the Ballarat Centre Against Sexual Assault, in Sebastopol, on 5320 3933, or free-call the crisis care line 24 hours on 1800 806 292.

Or phone Lifeline on 13 11 14, the Blue Knot Foundation on 1300 657 380, or Relationships Australia on 1300 364 277.