Their 29-year-old mother is expected to be charged with two counts of leaving a child unattended.
The Springvale Shopping Centre incident is the latest incident of children being left in hot cars.
The RACV, Victoria's roadside assist organisation, on average receives five calls a day to rescue kids from hot cars. Statistics are similar across the rest of the country.
Earlier this month, a five-year-old girl found in a car parked in the driveway of a home in NSW's Hunter Region died in hospital.
Natash Gorjup had been flown to John Hunter Children's Hospital and placed in an induced coma after being found unresponsive in the vehicle outside the Tanilba Bay house, in Port Stephens, on November 26. Temperatures had hit 35C in the region that day.
She died on December 1.
And in late November, two sisters – aged one and two – died inside a station wagon parked on the front yard of a family home in Logan, south of Brisbane.
The lifeless bodies of Darcey-Helen, 2, and Chloe-Ann, 1, were found inside the hot car on a day when the temperature in the area was 31C.
Their mother, 27-year-old Kerri-Ann Conley, was charged with two counts of murder.
Police across the country continue to issue warnings about leaving children in hot cars.
In 2018, NSW Police warned that on a typical Aussie summer day temperatures in cars could easily reach 60C.
"On a typical summer day, the temperature inside a car (even with the windows rolled down a little) can quickly rise above 50 to 60C," police said.
"Even on a relatively mild day, the temperature inside a car can get above 40C."
NRMA spokesman Peter Khoury earlier said most often parents leaving their kids in cars was unintentional.
"The majority of those cases are actually not intentional," he said.
"So, the mum or dad are putting the groceries in the boot of the car and they'll put the baby in first and give them something to play with – but the child ends up pushing the button and locking themselves in the car. When we attend, the parents are usually more distressed than the child.
"Having said that, there are a large group of people leaving children in cars intentionally and walking off and, more often than not, it's a passer-by that sees the child."
Mr Khoury said the danger of leaving a child in a car couldn't be overstated – adding that temperatures can double inside a car within five minutes.
"Sometimes, it's a case of someone running in to get a coffee and even that is extremely dangerous," he said.
"It just takes minutes. There's no airflow in the vehicle. Children and pets become dehydrated and distressed within minutes, and it doesn't take long for organ failure to kick in.
"Unfortunately, we have seen cases around the world and in Australia where children have died and it's due to organ failure and dehydration.
"Cars are not meant to be used as babysitters. Your car could also get stolen, someone could break in – so you shouldn't leave your child in the car at any time, regardless of the weather."
