Three days after being thrashed 5-0 at Moenchengladbach in the second round of the cup, Bayern bounced back with two quick goals as Lewandowski converted an early penalty, then drilled home a free-kick.
Bayern ended Union’s record of 21 league games unbeaten at home as Leroy Sane, Kingsley Coman and Thomas Mueller also grabbed goals, while Julian Ryerson and Niko Giesselmann scored for Union.