Make sure you try currywurst in Germany. It's basically a hot dog with tomato sauce (ketchup) and curry powder. Tastes brilliant and only costs 1 or 2 Euro.
I went on two tours alone...I made life-long friends along the way! That's the nature of Contiki.
Christmas Markets in Vienna are great. Buy some mulled wine (Gluhwein in German)which is served hot and is quite spicy. The mug it comes in is yours to keep - a great souvenir -but if you don't want it return it and get your €2 deposit back (Pfand).