"What to eat tomorrow" in Engpsh can be written as "What shall we have for tomorrow's meal?" or simply "What's for tomorrow's meal?"
Here's a sample sentence: "I was wondering what's for tomorrow's lunch?"
The usage of the phrase "What's for [mealtime]" is a common colloquial expression in Engpsh-speaking countries, often used informally to inquire about the planned menu for a specific meal.