Zwieback is a crispy, sweetened bread made with eggs and baked twice. It is sliced before it is baked for the second time, which then results in a crispy, brittle slice that closely resembles melba toast or rusk.
Medicinally, Zwieback is very good for upset stomachs, as it absorbs acid.
The Brandt Zwieback has a 99% name recognition in Germany; even more than Coke!