For recreation ...
The Internet portal of the Bavarian Cycle Network (Bayernnetz für Radler) provides extensive information on the subject of cycling in Bavaria. Thanks to a collection of nearly 120 cycling routes all over Bavaria and an online route planner, a weekend excursion out into nature can be planned quickly.
... and for every day
In Bavaria, it’s easy to combine cycling with local public transportation - for recreation as well as for the daily commute to school, to university, to work or to go shopping. There are bicycle parking areas at most train stations, light rail and underground stations. Additionally, you can also take your bike on nearly all regional trains (website in German).
Hiring a bike
In addition to the classic bicycle hire that bicycle dealers usually offer for tourists, most larger Bavarian cities are also increasingly providing public bicycle hiring systems. This, too, could be an optimal supplement to public transportation.
The German rail service Deutsche Bahn offers the "Call a Bike" hiring service (website in German) in Augsburg, Bamberg, Erlangen, Ingolstadt, Munich, Passau and Würzburg. After registration, you can hire a bike at any time. Some cities, like Nuremberg, also have their own bike hire service (website in German).