Also for Yesss there are many Hofer shops all over Austria. They are a discount supermarket chain that sell groceries and always have many weekly non-grocery specials. If you to to
Hofer - Filialstandorte and put in "Wien" in the second box where says "Ort" it will show you the locations of every Hofer Store in Vienna. (there are 20 listed in Vienna) Likewise, you could put "Graz" in there and you will find there are 20 in the Graz area as well. I am sure there will be one within easy walking distance of your hotel.