This week, Pahi had an extra 70 days added to his jail term after admitting the assault at a district court session heard inside the men's prison.
The court heard how Pahi and two mates were caught "highly intoxicated" on September 4.
Yesterday, Rolleston Prison manager Mike Howson revealed how they managed to get drunk while behind bars.
"Last month, staff noticed three prisoners appeared to be intoxicated," he said.
"It was found that the prisoners had foolishly consumed hand sanitiser."
Alcohol is a contraband item in prison, and any prisoner found making or consuming it faces disciplinary action.
A Department of Corrections spokeswoman said a number of processes were in place in jails to detect contraband, including daily random cell searches.