The 39-year-old was suspended for the second-round match at Lübeck, and possibly this weekend's Bundesliga game at Eintracht Frankfurt, after club officials heard he attended last Saturday's festival opening without telling them.
“That evening, I drank only half a Radler [a beer and soda mix] and then mineral water after that," Lehmann told Bild newspaper. “I drove myself home later on.”
Lehmann was at fault in Stuttgart's 2-0 league defeat to Cologne, who picked up their first win of the season last Saturday.
He gifted Cologne their second goal when he raced out of his area only to lose possession and allow Willy Sanou to shoot into an empty net. Coach Markus Babbel said he will talk to the ex-Germany star about the unauthorised beer outing.
“On Thursday, Horst Heldt [Stuttgart's team manager] and I will talk to Jens about this thing and we will see what happens after that,” said Babbel.
Lehmann seems to have accepted his punishment.
“The visit to Oktoberfest was for a charity event which had long since been planned, but had not been agreed with the club,” said the ex-Arsenal stalwart. “Of course, I accept the measures the club has taken.”