The Cologne University Sports Department has numerous options for trying out a wide range of different sports, free of charge (with a few exceptions).
'UniSport' also offers a diverse programme of activities. Their Sport Card costs EUR 15 per semester and allows you to attend countless courses at no extra charge. You may have to pay a participation fee for some individual events, but you won't need a Sport Card to take part in these.
In Aachen, the range of courses provided by the University Sports Department of the RWTH Aachen is open for use by all students. Many of their courses are free of charge.
In Wuppertal, there is also a range of courses provided by the University Sports Department of the Bergische University of Wuppertal. You can take part in courses there as a guest with special conditions.
The Support Office organises a sports tournament once a semester. This is a chance for students to test out their sporting skills against one other in a range of different sports.