I agree that it's not a big deal. I am also in Germany and around here some people refer to Caro Kaffee (that's a grain based coffee alternative with no caffeine) as children's coffee. We give our son (2.5) "Babyccino", which is just steamed milk, in a little espresso cup and it's just so cute, he can feel like he's drinking coffee like the adults but it's not coffee. I would view the beer thing in the same way. Of course even non-alcoholic beer has a wee smidge of alcohol in it so I would limit it to a tiny glass and yes, as a special treat.
I understand your husband's concerns. And it's true that when beer drinking is just a normal part of everyday life and a child sees that, it can grease the wheels for becoming an alcoholic as an adult or teen. But unless you and your husband are drinking every day at home....your daughter will not get the idea that alcohol is just a part of everyday life. Keep it as a special treat. Here in Germany beer is a part of life whether or not we like it and you might as well educate your DD now that it is a special treat and ok to drink in moderation....and model that yourselves as her parents and make it clear that until she's 16 (that is the legal drinking age for beer in Germany) she will be getting the non-alcoholic version. In this country she is going to be offered beer and have her peers drinking it starting at 16 if not earlier. Might as well be very clear about "this is how we drink beer", meaning "beer is for special occasions", and if she has a non-alcoholic beer every few weeks I think that is modeling responsible drinking. May seem like an odd lesson for a toddler, but I think it's better than acting like beer is "strengstens verboten", as that may trigger alcoholism even more as she may decide to drink earlier and more than she normally would, just to rebel.