Newcomers to Vienna are often surprised to find that nearly all retail establishments are closed on Sundays by law. Exceptions are made for train stations and airports. Therefore, most larger train and U-Bahn stations, as well as Schwechat airport, have small convenience grocery stores in them with staples such as milk, bread, and of course, beer.
Full-size Billa grocery stores can be found at the Praterstern and Franz-Josef Bahnhof stations on the U-Bahn.
A full-size Billa is also open at the airport on Sundays and there is a small Spar at AKH (suggested by Jennie!)
If you know of additional places to buy groceries and/or other essentials on Sundays in Vienna, please let us know at firstname.lastname@example.org.