Without the question mark, it is simple...
Can we make it in one hour — as I want to eat my dinner now.
(I like the dash as a clear separator for the question and statement parts of the sentence)
Adding a question mark, it looks wrong to me in all permutations. What should I be doing with this?
Can we make it in one hour as I want to eat my dinner now?
Can we make it in one hour? as I want to eat my dinner now.
Can we make it in one hour — as I want to eat my dinner now?
Can we make it in one hour? — as I want to eat my dinner now.
