"Do you eat a sandwich or soup?"
Translation:Jesz kanapkę czy zupę?
It's not completely impossible, but I'd interpret it as "Are you by any chance eating a sandwich or soup now?" and even then, 'albo' instead of 'lub' would feel better to me, even though they're rather totally synonymous. Plus adding "może" after "jesz" would make us sure that this is this interpretation, thus creating a sentence that sounds more or less natural.
"Zjesz (może) kanapkę, albo zupę?", using perfective, makes a lot more sense, as it means "Will you maybe eat a sandwich, or soup (or maybe both)?" It's not an A/B question 'what will you eat', it's a proposition (from a grandma to a grandchild, most probably :P)