He appeared before Judge Geoff Rea in the Napier District Court on Friday for sentencing on one charge each of aggravated robbery, possessing methamphetamine utensils and receiving stolen property.
The judge told the court it was another "very sad" case of a young person getting himself into a situation, probably through drugs, where they committed serious offending.
He said the woman had "feared for her life" and undoubtedly suffered as a result of the robbery.
The strongest indicator that it was a planned attack was the fact he had brought the shoelaces he eventually used to tie the woman up with him to the dairy, the judge said.
"Whether it is the drugs that are making you do it I have no idea at all but I hope you've had an opportunity to reflect on the terrible position you've put this woman in."
In explanation, Apatu had told police he committed the robbery to get money for his partner's birthday.
Defence lawyer Eric Forster told the court his client had made friends with his neighbours who were "significant players" in the distribution market of methamphetamine in Napier.
"He's become heavily addicted and done something completely out of character. He's a person with good prospects and has good family support."
He said the offending had "devastated" his family, some of whom were sitting in the public gallery, and submitted his client should get a discount for his remorse and early guilty plea.
Judge Rea passed a sentence of three years and nine months' imprisonment, which reflected a 25 per cent discount for the guilty plea.
It was the courts' responsibility to send a strong message to the community that this type of offending wasn't tolerated, he said.
He ordered the destruction of the knife but could not order the defendant to pay reparation due to his jail term, saying "once again the complainant misses out".
At the time of the arrest, Detective Amy Bryant said crime prevention wasn't something police could do alone, requiring commitment and support from the community.
"Crimes such as this are unacceptable as they have a serious impact on small business owners and communities.
"Police are committed to working with the community to prevent crime, however should a crime be committed they work tirelessly to hold those responsible to account."