Even if you are a guest, meaning you are neither a student nor an employee, payment in cash may still not be possible. You may have to get a guest card at a guest card machine and pay with it at the cash registers.
Such a machine can be found in the foyer of the Am Adenaurring Dining Hall at the entrance of the Update/Linie 6. In the other dining halls, you can receive a guest card at the cash registers.
Unlike at our dining halls, cash payment is possible in our cafeterias.