I submitted "You don't want bread?" and was corrected to "You wouldn't like bread?" which sounds like the wording a British person might choose to convey the same intent. Sorry to say, I'm American (believe me, we'd rather have bread for president than Trump)
On this discussion page, the translation is currently "Do you not want bread?" which seems generally equivalent to "Don't you want bread?", so I'm not really sure why my answer was excluded.
In theory you're right, "you don't want bread?" should be an acceptable form when asked as a question, but you might have noticed they Duo seems to ignore punctuation. The form "you don't want bread" is taken as the statement of fact, i.e. I'm telling you that you don't want bread. The question form is usually phrased in Duo's answer bank with the inverted subject "don't you want bread" and similar variations.