I thought both were right, but Duolingo is so inconsistant when it comes to this part of grammar. In addition, my "no meu café" was judged wrong, which is very annoying. But I shouldn't rant about that to you, of course.
Well, either Brasil has changed a lot, this is not a Brasileiro speaking, or they are lying. When I grew up in Brasil, way back in the 60's, there was no such thing as coffee without sugar. Ai que saudades!