I just went to Biergarten about two weeks ago. I asked the waiter if there were any sugar-free desserts on the buffet. He told me there weren't any out, but he might have some sugar-free cheesecake in the back. He came out a moment later with a massive slice, and I thoroughly enjoyed every bite! (This coming from someone who formerly didn't think she liked cheesecake!)
While eating at the ABC Commissary in DHS, I found a "no sugar added" parfait, with some kind of custard, strawberries, and cream. It was pretty good too, though not as good as that cheesecake in Germany, in my opinion.
I believe the bakery in Norway also has a "no sugar added" chocolate mousse, though I've never tried it.
Yes, you do have to watch the carbs in a lot of food because other carbs can affect blood sugar levels, not just sugar... and "no sugar added" doesn't mean "no sugar" or "no carbs," but it still is probably less than similar full-sugar desserts.
It somewhat depends on an individual's body-type, but all the walking you do in the parks, combined with eating protein along with carbs, can help maintain lower blood sugar levels. (I basically ate just meat at the German buffet - all protein - before having that cheesecake, which may have helped.)
I learned a lot while I had gestational diabetes and did tons of research.
Now I've begun a low-carb way of life and have done more research. If I'm going to have an occassional treat, I'll try to have something "low sugar" or "no sugar added."