Preheat the oven to 350°F. Generously coat a 12-cup muffin pan with cooking spray.
In a medium bowl, whisk together the eggs, egg whites, granulated garlic, onion powder, salt, and pepper until well combined.
Cook the spinach according to the package directions. Transfer it to a mesh strainer and squeeze out as much liquid as possible.
Divide the spinach evenly among the muffin cups
Divide the drained tomatoes evenly among the muffin cups.
Add 1 tablespoon of feta cheese to each muffin cup.
Pour the egg mixture evenly into the muffin cups, filling each cup almost to the top.
Give each cup a gentle stir to distribute the ingredients.
Bake for 20-22 minutes, or until the centers are set.
Let the egg bites cool for 5 minutes before removing them from the muffin pan. Run a butter knife around the edges and gently lift them out.
Serve immediately or store for meal prep.