From Twitter:
What’s the usual expression?
① What did you have for lunch?
② What did you chow for lunch?
③ What did you eat for lunch?
④ What did you had for lunch?
The answer and explanation is: ① ‘What did you have for lunch?‘ We don’t usually say ‘eat’ (choice ③) unless we want to focus on the physical act of consuming food or unless the listener(s) did not hear ‘have’ after several attempts to ask.