In individual cases, the house rules may prohibit the visible airing of bedding or the hanging of laundry on Sundays. This includes hanging laundry (or bedding) by the window or on a rotary clothes dryer or on a line high up. However, nobody can prohibit you from hanging laundry in an area that is not visible, for example on a clothes horse that is shielded by the balcony railing. Incidentally, this is always permitted, even if a tenancy agreement generally prohibits drying laundry on the balcony (not just on Sundays). It is also permitted to install a privacy screen (for example, if the balcony only has a railing) or a parasol.
More information on the topic of balconies in tenancy law HERE!