It wasn't until three hours later that two pool contractors found the baby, wearing a heavy jumper, pants, socks and a one-piece polyprop.
The contractors knocked on the back door and saw the defendant sitting on the couch, unresponsive, before they realised the infant was in the car beside the house.
As they opened the door the car the baby immediately began screaming. They noticed the car was uncomfortably hot and the distressed baby was red and sweaty.
The men took the baby, his clothing full of sweat, out of the car and began cooling him down by removing the garments and dabbing him down with cold water.
They called an ambulance and again tried to get the defendant to come outside but he struggled to open the back door and, when he finally did, he looked at the men blankly and returned inside.
Ambulance staff treated the baby, who was extremely dehydrated and had an accelerated heart rate. He showed early signs of shock but was not hospitalised.
Police found two empty vodka bottles in the garage, beside an empty beer can.
Stewart told police the last thing he recalled was taking the empty vodka bottle to the garage before having a lie-down on the couch.
The man was charged with child neglect and found guilty at a judge-alone trial last month.
Yesterday Judge Tony Adeane sentenced him to 12 months' intensive supervision and 150 hours of community work. The maximum penalty is 10 years' imprisonment.