The name of the 18-year-old can't be revealed because he was 16 when he was charged with arson following the March 2013 blaze.
A judge has given him six months of deferred custody, followed by 18 months of supervised probation.
Deferred custody under the Youth Criminal Justice Act is equivalent to a conditional sentence given to adult offenders.
Court heard he had been admitted to Children's, but slipped away from his ward and lit two fires in a nearby construction site, triggering the evacuation which included more than 100 patients.
The teen says he can't remember starting the fire.
The court was told the accused was admitted to hospital because his mother suspected he had overdosed on drugs, appeared to be having seizures and was possibly suicidal.
He lit two separate fires, one of which sent smoke billowing into the adjacent hospital. Security staff found the teen soon after with a cigarette lighter. He was also spotted on surveillance video in a hospital stairwell.
The teen tearfully told a probation officer he "felt horrible" about what happened.
"I did something like that to a bunch of innocent kids. They didn't deserve that," the accused told the officer.
The fire was at the site for a planned $59-million diagnostic imaging centre. Crown prosecutor Mike Himmelman said the most recent damage estimate pegged the overall value of the blaze at $7.2 million, not including the cost of any construction delay. (Winnipeg Free Press)Suggest a correction