Actually, that sentence is grammatically incorrect. English either follows the common romance/germanic question-formation grammatical structure of reversing the positions of the subject and the verb (i.e. "You are eating" --> "Are you eating?") OR it starts the question with an otherwise untranslatable question word (i.e. "Do you eat?"), depending on whether or not you're working in a continuous tense.
I disagree. It's very common in colloquial English in any case, though more typically as the contraction "you're" instead of "you are." Eg. "You're going too?" "You're getting married?" Granted, it sounds a little stilted as "You are going too?" but I wouldn't argue it as incorrect. And in this case, the "or" makes it sound a little more odd, but it's still possible to construe it as grammatically correct, if a bit of a stretch. "I am eating only fruits that ripen in autumn." "Oh, you're eating apples or pears?"