A standard venue for a non-vegetarian lunch is "Lanse", where you can have a lunch for 18 PLN.
For vegetarians, there is a choice of eastern cuisines, and Loving Hut, a vegan bar. Sometimes both vegetarians and non-vegetarians go to an Indian restaurant "Mandala".
People prefering to eat for lunch their sandwiches can use Club-Room 409 ( IM PAN, 4th floor).