Bayern moved closer to a record-extending 30th German league title with a 5-0 drubbing of struggling Fortuna Dusseldorf on Saturday.
Only Bayern's players and staff were there to cheer the kind of dominant win which would normally put Bayern fans in a party mood.
Lewandowski flicked his second soon after the restart and Alphonso Davies completed the scoring with a solo goal.
Earlier, Werder Bremen revived its hopes of avoiding relegation with a 1-0 win over slumping Schalke.
A lacklustre first half failed to produce any fireworks before Bittencourt unleashed a thunderbolt into the top corner from 25 metres in the 32nd minute.
"This is a very, very important away win", said Bremen coach Florian Kohfeldt.
"We have taken seven points from the last three games, but if you look at the table, we are still behind".
However, Saturday's victory leaves them just three points from guaranteed safety with six games left.
They are two points behind Duesseldorf in 16th, which carries a relegation play-off at the end of the season.
Schalke and USA national team midfielder Weston McKennie played wearing an armband referencing the death of George Floyd.
"We have to stand up for what we believe in and I believe that it is time that we are heard!"
His protest came in the wake of Floyd's death in Minneapolis after a white police officer pressed a knee into the 46-year-old black man's neck for more than eight minutes on Monday.
Elsewhere, Javairo Dilrosun's cute finish midway through the first half set Socceroo Mathew Leckie's Hertha Berlin on their way to a 2-0 win over Augsburg, who remain in relegation danger.
Ten-man Frankfurt gave Wolfsburg a shock after registering a 2-1 victory at Volkswagen Arena.
France defender Benjamin Pavard took centre stage when his scuffed shot led to Mathias Joergensen's own goal after 15 minutes before Pavard made it 2-0 just before the half-hour with a header that keeper Kastenmeier got a hand to but could not keep out.
Frankfurt were on the back foot at the start but struck against the run of play when Portuguese Andre Silva was brought down in the box and converted the 27th-minute penalty himself.
Japan midfielder Daichi Kamada scored the victor 10 minutes from time while Frankfurt had replacement midfielder Lucas Torro sent off in the dying stages for a second yellow card.
In Mainz, Hoffenheim substitute Ihlas Bebou scored with nearly his first touch as they beat Bundesliga strugglers Mainz 1-0 to boost their hopes of qualifying for Europe next season.