The ARU said Haylett-Petty had been found guilty of urinating in a public place, while Cowan gained "unauthorised access to a team vehicle" after he missed a team curfew.
"I was very disappointed with the way I acted and let the team down," Haylett-Petty told Fox Sports on Sunday.
"I'm really looking forward to trying to make up for it. Hopefully my actions speak louder than my words."
Local media had reported the ARU's integrity unit had investigated the Force for a series of incidents, including a scuffle between players that damaged a hotel vase which Haylett-Petty paid for.
New Zealand-born Cowan had assumed the captaincy of the struggling side after Matt Hodgson suffered a season-ending shoulder injury. Haylett-Petty was vice-captain.
Both played in Saturday's 22-3 loss to the Stormers in Perth, though winger Luke Morahan captained the side.
"They apologised and we accepted that, and we moved on pretty quickly as a group," Morahan said.
Interim coach Dave Wessels, who replaced Michael Foley after he was sacked last month, added the incidents had been out of character, especially for Haylett-Petty.
"Dane in particular has been very embarrassed and very apologetic all week," Wessels said.
"For him, it's just a one-off mistake. It's important people understand it's certainly not a trend. Dane is a very special part of this team."
The Force, who were recently bailed out of financial strife by the ARU, are bottom of the Australian group with just two wins this season.
The side have managed a winning record in only two of their 11 seasons since joining the southern hemisphere competition.
They finish their season next Saturday in Canberra against the ACT Brumbies.
(Reporting by Greg Stutchbury in Wellington; Editing by Mark Lamport-Stokes)
