Could this be the matching German hat?
It is highly likely, as here's a semi-stock art Sonic, altered to be holding a bottle of Coca Cola (instead of the cup). If you notice, you can see his other hand is also open on this one as well, further linking the images.
The art on the red baseball style cap is embroidered on, and the detail seems just fine. You can see the white stitching on the cola bottle. Thought to be given to Sega Europe employees. The interior says "Enjoy Coca-Cola Clothes