If you are in Stuttgart without a bike but would like to get around town on two wheels, you can hire a bicycle.
Deutsche-Bahn subsidiary DB Rent operates under the name Call a Bike - they have 400 hire bikes available at 65 locations in the city centre and districts West, South, North, East and Bad Cannstatt. The special thing about their service in Stuttgart is that the first half hour of cycling is free. You can easily get from A to B like this and then leave the bike at one of the many stations. All you need to hire a bike is a mobile phone.