Sami Khedira lamented the "unnecessary, stupid defeat" to England and admits Germany must "take a look at themselves" in the aftermath of the loss.
England stunned the world champions in Berlin on Saturday night after overturning a two-goal deficit to come back and win, the first time they had achieved the feat in almost 40 years.
In-form strikers Harry Kane Jamie Vardy brought England level before Eric Dier's stoppage-time header completed a famous 3-2 win at the Olympiastadion, leaving the hosts shell-shocked.
"It was an unnecessary, stupid defeat," Germany midfielder Khedira said. "We all need to take a look at ourselves and work hard now.
"We did a lot right up until the second goal, then after that we were much worse - and England punished us.
"However, we played well for an hour. We need to play well for 90 minutes against Italy (in Tuesday's friendly) and in the European Championship."
Besiktas striker Mario Gomez, who scored German's second on the night, felt the hosts should never have let England get back into the game after leading 2-0 with half an hour left to play.
"It is somewhat inexcusable," Gomez said of the loss. "We were playing very well until we were 2-0 up but we didn't use enough of our chances.
"Afterwards, we stood off our opponents too much and England are very strong from set-pieces."