Maroni sind um Klassen besser als die ErdäpfelpufferMaroni (roasted sweet chestnuts) are very popular in autumn/winter in Austria. They are sold from little booths on street corners and markets.
Authentic Austrian streetfood unfortunately is slowly being replaced by Kepab or China noodle booths… but they are still around. Nothing is better than a "Käsekrainer" (sausage filled with cheese) with lots of mustard at a "Würstelstand" when it is 4 AM and you're drunk as hell:
My favourite is the "Leberkäsesemmel" (= type of meatloaf, I guess. A literal translation would be liver-cheese…). You can get that also at almost every bigger supermarket: