The conviction leaves the pair liable for civil claims by the insurance firms.
However, Day was due to leave the country for Melbourne at 4pm yesterday and Noar for Asia this morning.
"I accept it was not a deliberate action on your part to damage the pipe," Judge Michael Turner said.
"However, you have pleaded guilty on the grounds of recklessness that when during your festivities you swung on the pipe, you must have appreciated that damage could have been caused to the pipe but carried on regardless," the judge said.
Lawyer Sonia Vidal told the court Noar and Day, who were working for accommodation at Nomads, had been to each business and apologised in person.
"They are very remorseful for their actions and had no appreciation their foolishness would have this impact," Ms Vidal said.
Firefighters were called to Nomads shortly after 4am on February 14, when water flooded through the budget hostel and down into Cup & Cake, Devil Burger, Below Zero Ice Bar, Cowboys Bar, and a convenience shop.
Attempts yesterday to contact the owners of businesses affected by the flooding were unsuccessful.
The building's insurer, QBE, did not respond to questions by deadline last night.