Mr Sipaia did not see the punch coming, and fell instantly to the ground.
Various witnesses described it as a king hit, big swing and cheap shot, Justice Collins said.
"Yours is a case where serious injury was intended."
Justice Collins said Ioata had a troubled background and problems with alcohol.
"Sadly you are typical of many young men in New Zealand."
Through tears, Mr Sipaia's widow, Fei, read her victim impact statement to the court. She explained they had been married four years when Mr Sipaia died.
"I have found myself struggling to deal with it emotionally. I'm always a happy and cheerful person, so when I see people I always smile, but deep down I am always hurting."
She said when she looks at her children her heart breaks.
"It hurts knowing that I have lost the love of my life," she said.
But she went on to say she held no hate towards Ioata.
"I just wish you never did what you did. I forgive you for your actions that night."
Mrs Sipaia also read a victim impact statement on behalf of Mr Sipaia's mother, Nuuao, who also forgave Ioata.
"Why have you wasted your life? In my humble heart, in front of God ... we forgive you and the others involved in his death."
Following the sentencing Ioata and Mr Sipaia's family crossed the court room to hug each other.