今朝ぶどうを食べましたか？って英語でなんて言うの？

Explanation: We rarely use the word 'eat' in relation to food. 'Have' is the preferred verb when talking about consuming food or drink. A typical non native error.
Example sentence:
"Have you had lunch yet."

You can sometimes use 'have' or 'had' in place of 'eat' or 'ate', for example:

"I am going to have the chicken"
"I didn't have lunch today"
"I want to have dinner now"
"I had a great breakfast"

Native speakers will say like this: “Did you eat grapes for breakfast”.
There are lots of other ways to say it, but this one is the most accurate and most commonly used.
Here is an example on how to use this in a conversation:
A: Did you eat grapes for breakfast?
B: No, why do you ask?

Breakfast is the first meal of the day usually in the morning once you have woken up so you could ask 'did you have/eat grapes for breakfast?'

When wondering if someone ate grapes for their breakfast, you can say in a casual way, "Today, did you eat/have grapes for breakfast?"

Native speakers often use the two words 'eat' and 'have to mean the same thing, especially when the conversation is about food. These two sentences are extremely common and probably the most natural for native speakers. It asks a simply question and does not require a long, complex sentence, so it is easier and quicker to say.