After responding that you had breakfast, you can ask the person the same question in a polite and friendly manner. Here are a few ways to do it:
"Yes, I had breakfast. How about you? Did you have breakfast too?"
"Thanks for asking! I had breakfast. Did you manage to have yours?"
"Yep, had my breakfast already. How about you? Did you have breakfast today?"
"Yes, I did. What about you? Did you get a chance to have breakfast?"
"Breakfast was good! How about yours? Did you have breakfast yet?"
Remember to maintain a friendly tone and show genuine interest in their response. Asking about their breakfast shows that you are engaging in conversation and care about their well-being.