Programmers know :) : an "inclusive" or is when one or BOTH sentences can be true. "Exclusive" or (usually "xor" in programming) is when either one or the other sentence is true but NOT BOTH. In Romanian, an exclusive or is marked by doubling the word (sau/ori): "Bei SAU apă SAU lapte" (that means you have to choose, there can't be both). When there is a single SAU (or ORI) it usually means an "inclusive" or (but leaves room to some ambiguity).
Put it this way: Do you love your mother or your father? You're not necessarily limited to strictly only the one or only the other. As the meme goes, "¿Por qué no los dos?"
Where do I find the prepositions, etc.? The pictures only give the nouns. I am guessing the verbs because they are similar to Italian.
Later: OK, I have discovered that everything is there, I just need to move the cursor over the sentence on the left. I guess I was going too fast.
Sorry if this sounds stupid but why wouldn't this be "Are you drinking water or milk"? Besides the fact that the sentence itself doesn't have a question mark, if you did add one could it be a correct question? (This is a bit confusing ;-;) Honestly this sentence doesn't make much sense having "or"/"sau". It would have been better with "and".
For some reason the Romanian tree doesn't ever allow me to answer in Romanian writting.