The versatile midfielder has urged his team-mates to up their game ahead of their Bundesliga opener against Borussia Monchengladbach
Goals from Xherdan Shaqiri and Arjen Robben plus a Thomas Muller hat-trick helped the cup holders to a comfortable away victory.
However, Kroos was by no means satisfied with his side's performance against the Oberliga outfit and has urged them to up their game ahead of the start of the Bundesliga season.
"We made a lot of mistakes during the game and often lacked focus," Kroos was quoted as saying by Bild.
"We cannot afford to play like this against teams with more quality. They will definitely take advantage of these kinds of mistakes."
Bayern kick off their league campaign on Friday with a home match against Gladbach.