I made a rookie mistake in a little diner near Neuschwanstein Castle. I didn't read the ingredients on a packet of mustard. I know better, but the chef had said it was gluten free, and I didn't check, even though it was still in a packet with the ingredients on it. It wasn't even in German. So I did get slightly sick from the mustard, which I belatedly realized had beer in it.
The meal wasn't great either. After difficulty communicating with the waiter, I told the chef I didn't care what he brought me, as long as it was gluten free. So I got greasy bratwurst with mustard that wasn't gluten free.
If you are looking for a place to eat near Neuschwanstein Castle, I can't recommend Allgauer Stuberl in Hohenschwangau village. If you know of a better place near there, please post!