I have not yet visited Germany but 2 of my friends did in 2008-09 (separately), Christophe Belzile and Julie Mainville, and they brought me back a t-shirt for my collection.
Here are a few pictures of the Hard Rock Cafe in Cologne:
Here are my t-shirts from Hard Rock Cafe Cologne:
I encourage you to also view all my Hard Rock Cafe pictures here of t-shirts and locations. Also please check out my post on Montreal’s Hard Rock Cafe that is now closed. Follow this link if you want to see the complete collection of my Hard Rock Cafe posts up until the end of 2012.