For months in Mainz, a small American-style donut shop (the Tasty Donuts and Coffee Shop) tried to make it near the Romer Passage, and I noted yesterday.....it'd finally shut down. There just wasn't enough interest or business.
Germans aren't really donut-minded. Toss in the profit margin and it really does take an element of luck to succeed.
But as I transited through the Wiesbaden train-station yesterday.....I noticed a brand new Dunkin-Donuts operation in the big hallway. It'd been an empty shop for months.....and some grand opening was underway yesterday. Twenty-odd people were lined up and they were brisky selling donuts. It's a high-traffic area and might succeed (high costs involved for the location though).
There are American trends that simply won't make it well in German business. It's like taking some German trends which do well here in Europe.....but just won't go well in the US.
Right now in the Wiesbaden train-station, there are three morning-food item shops in existence already (before Dunkin-Donuts opened). I'd take a guess that forty-thousand people transit in or out of the train-station each morning. Maybe twenty-percent will buy a coffee on the way, and maybe half of the coffee-drinkers will buy some pastry. The issue I see is that travelers in this facility drops off drastically on Saturday and Sunday, and by mid-afternoon on work-days....these Dunkin folks will see almost nothing going on.