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
“Other creatures receive food simply as fodder. But we take the raw materials of the earth and work with them—touch them, manipulate them, taste them, glory in their heady smells and colors, and then, through a bit of alchemy, transform them into delicious creations.”
― Judith Jones, The Tenth Muse: My Life in Food