While Betterlife (formerly known as Reformhaus Bacher) can be very good to get something to eat in the otherwise not very vegan-friendly main station, you definitely have to watch out and read the labels.
However, they have definitely seen the signs of time. When I wrote my first review of them some 3 years ago, I was diasppointed because most of their fake meat products still contained dairy. Now thay have a wide range of vegan products.
They also have good full-grain bakeries and know which of them are vegan. Highly advisable if you do have a little time at the Hannover train station.Pros: Many vegan products, good full-grain bread
Cons: some fake products contain egg/dairy