nine points clear at the top of the Bundesliga.
Kevin Trapp made a number of excellent saves in the first half to frustrate the visitors, keeping out efforts from
Robert Lewandowski and Joshua Kimmich.
Sane made the breakthrough when he ran on to a through ball towards the end of the second half and fired home.
Eric Maxim Choupo-Moting was denied adding a second late on.
Bayern take victory over Frankfurt on Sunday at Deutsche Bank Park.
Borussia Dortmund can cut Bayern’s lead on Sunday when they travel to Augsburg.