Travelling in Germany as a Vegan is a walk in the park! The Vegan lifestyle had a boost in the last 10 years and you will find many shops, Cafés or Restaurants catering for Vegans.
If you are on a budget or in self catering accommodation, those (organic) supermarkets will offer a huge Vegan variety:
You will find that supermarkets like Aldi, Lidl, Edeka, real etc. also offer a Vegan range.
Almost every Café will have a Vegan / Gluten Free option and being a travelling Vegan in Germany is no problem whatsoever! Whereas you’d be looked at as if you were an Alien 15 yrs ago, asking for Vegan options, it is very common today.
I am just travelling in Germany and went to a very ordinary, big Café / Restaurant today and found a Vegan Burger on the menu. I completed it with a self made Blueberry / Pomegranate Ice tea and had a most delicious meal.
There will be areas of Germany where being a Vegan can still be tricky (Bavaria or East Germany for example) but places like Berlin, Cologne and Dusseldorf are very Vegan friendly.
It is great to see how the Vegan market has grown!