Touch and hold a meal, then drag it onto another day. When you let go, choose Move or Copy. To move just one food, touch and hold that food instead — it goes into the same meal type on the new day. This works in the list of days on iPhone and iPad, and in the iPad Week and Month views.
Without dragging: open the day, tap ••• beside the meal’s name and choose Move or Copy. Pick the day in the calendar and tap Move or Copy at the top. Copy stays open so you can copy to more days. The same menu has Change Meal Type, Save as Template, Add to Calendar and Add Note.
To change the order of foods in a meal, touch and hold one and drag it up or down.