Having only been released on Monday from Landsberg prison, where Adolf Hitler wrote 'Mein Kampf', Hoeness joined wife Susi and Adidas boss Herbert Hainer in watching the league game against Mainz.
Hoeness resigned as Bayern president after being convicted in March 2014 of having evaded paying at least 28.5 million euros ($31.5 million) in taxes.
He has refused to talk about his future and says he wants to make a decision in peace with an announcement expected on July 1.
The 64-year-old's first official engagement will be a ceremony in Moenchengladbach on March 13 to honour Jupp Heynckes, who coached Bayern to the 2013 treble of Champions League, German Cup and Bundesliga titles.
Three days later, Hoeness is expected to attend Bayern's Champions League, last 16, second-leg clash at home to Juventus after the away tie ended in a 2-2 draw in Turin.