The 22-year-old New Zealand winger allegedly struck at least one patron in the bar before being escorted from the premises by friends.
Guildford issued a statement through the New Zealand Rugby Union, with the World Cup-winning wing voicing his remorse over the incident which occurred on the popular tourist island.
"Firstly, I would like to apologise for my behaviour here in Rarotonga on Thursday night," he said.
"I have no clear recollection of the events of that night but there is no doubt that my behaviour was unacceptable and I am hugely embarrassed by what happened.
"I want to apologise to the people who I was involved with and offended that night, the patrons and staff who witnessed my behaviour, and the Cook Island people. I am truly sorry for what I did.
"I also want to apologise to my family for the embarrassment my actions have caused.
"I don't want any sympathy for the situation I have ended up in, but I am thankful for the support I have received so far from so many people. It's obvious that I need help and I want to get home and to get that help as soon as I can.
"I need to sort myself out."
Guildford is not expected to lose his contract with the NZRU and the Crusaders despite general manager Neil Sorenson's admission the player had been disciplined over his drinking three times in the past 18 months.
The only publicised instance came in the wake of New Zealand's Tri Nations loss to Australia in Brisbane, where he was forced to front the media as reports of heavy drinking surfaced.
Sorenson said it was important to help Guildford, rather than cast him afloat, and the wheels can now be set in motion given the player's acceptance he must address the issue.
"We've got to establish the facts and it sounds like he got up to something. We are not denying that," Sorenson said.
"He lost his dad a couple of years ago. He's also had some alcohol-related issues in the past. He's a good young man."
All Blacks mental skills coach Gilbert Enoka is believed to have joined Guildford in Rarotonga to lend his support and start the process of his recovery.
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