It's been a long time since I have lived in Germany however, popcorn was not readily available...people liked it but corn was not served often as it was considered pig food ()...at the time I was there peanut butter was hard to find.
I think you couldn't go wrong with food products from your state...i.e. dried cranberries, chocolate covered dried cranberries...mustard wouldn't be a bad thing, especially one that is different, but they probably have mustard readily available...I did like the suggestion of a breakfast package with Maple Syrup.
Whatever you decide upon I am sure they will appreciate the effort you took...and you might find something they want again...
Have a good time and enjoy yourself, even if it is a business trip!
Grandma Pam to 3
Winter is the time for comfort, for good food and warmth, for the touch of a friendly hand and for a talk beside the fire: it is the time for home.”
― Edith Sitwell