According to the sentencing notes, the couple bought synthetic cannabis while in Auckland in December 2017 then drove back to Tokoroa with their children, arriving at 2am.
The pair parked near the Aquatic Centre to sleep overnight.
With the woman and two children asleep in the car, the man consumed synthetic cannabis using a plastic bottle as a bong, until he fell unconscious.
In sentencing the pair, Judge Tony Snell emphasised the family were in a confined space.
At 6am the next day, a passer-by saw the vehicle.
"You were both passed out from the effects of synthetic cannabis in your car with your children also suffering the effects of synthetic cannabis passively inhaled because they were in the car with you."
At 8.10am, after their swim, the person shouted and banged on the window before contacting police.
When police arrived, the man was still holding a bong. When the vehicle was searched, police found cannabis and synthetic cannabis.
"[The children] had dirty faces, mucus coming from their nose. [One child] was dressed only in a singlet with no pants or not even a nappy on," Judge Snell said.
Days later, the pair met again with their children and the man's sister.
After buying the children McDonald's, the couple began smoking synthetic cannabis again, prompting the man's sister to wind down the windows.
"You then drove under the influence ... to another address where you purchased another bag of synthetic cannabis before parking and consuming that."
The couple reached a point where the woman lost consciousness and fell forward in her seat and the man was heavily impaired and slumped backwards.
"Your [child] was crying and he was yelling at you, [the mother] and hitting you from behind, telling you to 'wake up, wake up'."
The man's sister called her parents for help.
Later, the parents described their son as "gone, but not dead to the world".
As the man began to sober up, he decided to drive his partner and their two children home.
"It is an appalling decision, endangering everybody, not just you and your partner and your children, but every other road user."
At home, nobody could rouse the woman and a cousin took the children, fearing for their safety.
"The two of you were left at that address, your children were taken away, you would not have had a clue who by."
Since the incidents, the children have been removed from their parents' care.
Judge Snell said it would be unknown for some time how the children had been affected by the synthetic cannabis they passively consumed.
In his sentencing notes, Judge Snell referred to two previous cases heard in the Rotorua District Court.
The first was a young mother sentenced to home detention in April last year, after she consumed cannabis until she was in a "zombie-like" state and could not care for her two young children.
The second involved a couple who were sentenced in September last year, after consuming synthetic cannabis in the Rotorua CBD. They had a 2-year-old girl strapped to a stroller, dressed in a heavy sweatshirt on the hot summer's day and were found in a semi-comatose state.
Their daughter was found to have insect bites and open sores. In that case, the woman was imprisoned for 10 months and the man, who also had an assault charge, for 19 months.
"You may wince, you may think that is appalling, but it is very similar to what you have done here," Judge Snell said as he sentenced the couple on December 7.
