Yes, "vous voulez boire" means "you want to drink"

And "you want to drink" means either "vous voulez boire" or "tu veux boire"

Because "you want to drink." is not a question but a statement.

I don't think so, but Duolingo says it is.

Yes it does and it is very frequent.

conjugation of verb "vouloir" (3rd group) = want, in indicative present:

je veux, tu veux, il/elle/on veut, nous voulons, vous voulez, ils/elles veulent.

Verb "vouloir" is constructed with an infinitive (and no preposition).

"Buvez" is a conjugated form of verb "boire", in 2nd person plural, ie "vous".

So, your proposal is wrong and in any event, whether you drink water or any other liquid, the sentence remains the same: "tu veux boire" or "vous voulez boire".