Overnight oats with protein powder and fruit, Chia pudding with fruit and Greek yogurt, eggs and whole wheat toast with guacamole or avocado, protein pancakes with fruit and Greek yogurt,
Something high in protein and with low glycemic index carbs.
You want something that will digest over a long time and release sugars and nutrients into the blood steadily, not something high in refined highly available sugars which hit the bloodstream all at once and spike blood sugar, then when it’s all used up your blood sugar dips back down sharply.