Hours before his team take on Barcelona in Spain for their Champions League semi-final second leg, Hoeness said the club had nothing to do with the account under investigation, which was used only for "stock market gambling" and financed by the late Robert-Louis Dreyfus, a former head of sports manufacturer Adidas.
"From 2002 to 2006 I was really gambling [with stocks]," Hoeness told Zeit newspaper. "I sometimes traded day and night with sums that are now difficult to comprehend. Some of those amounts were extreme.
"This gave me a kick, pure adrenaline," said Hoeness, who has been under mounting pressure to step down.
The former Bayern player and long-time club general manager is under investigation for tax evasion after he filed a complaint against himself earlier this month. There are no details of the amounts in question.
Authorities can offer some leniency in cases where individuals name themselves as tax evaders.
Hoeness, whose professional as well as personal reputation has been damaged by the affair, said his house had been searched in March as part of the probe.
"My life changed on March 20 at seven in the morning. I stood there in a bathrobe and the prosecutor was at the door. That is when hell started for me.
"I made a huge mistake which I want to try and correct as much as possible," said the outspoken Hoeness, who could face a jail sentence depending on the amounts in question.
"I feel I have been catapulted to the other side of society. I made a mess of it but I am not a bad person."
The affair comes at a time when Bayern, the club Hoeness has served for more than 40 years is bidding to win an unprecedented treble of titles for a German club of Bundesliga, German Cup and Champions League.
Hoeness, facing mounting calls to resign, said he began gambling bigger amounts before the dotcom bubble burst. But after it burst he had been given money from the late Dreyfus in 2001.
"He said 'let's do something together', he would finance it," Hoeness said.
"That is how the millions came on to the account. It was always clear it was an account for [stock market] gambling. This account was only Uli Hoeness."
He said the 2008 financial crisis led him to gamble much less.
"I am also now older. I am 61," Hoeness said.
