Preheat your oven to 350°F (175°C).
Grease the muffin tin with cooking spray or olive oil.
In a large mixing bowl, crack the eggs and add milk. Whisk until well combined.
Stir in the chopped spinach, sun-dried tomatoes, and crumbled feta cheese into the egg mixture.
Sprinkle in garlic powder and onion powder, and add salt and pepper to taste.
Pour the egg mixture into the prepared muffin tin, filling each cup about 3/4 full.
Bake for 20-25 minutes, or until the muffins are set and lightly golden on top.
Allow the muffins to cool for a few minutes before removing them from the tin.