Is there a specific rule about the word order of questions?
It's usually verb-subject-object, and possible interrogative pronouns start the question.
so, "Manden drikker maelken?" in that interrogative order is also OK?
You can say that but it is not used much. If you say it like this your tonation goes up in the end of the word to indicate it is a question.
It is sort of like ing german the logic (the verbs in second place)