Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish with butter.

Cook bacon in a skillet on medium heat until golden brown, about 8 minutes. Remove and chop coarsely.

Cook sweet potato, broccoli, onion, and garlic in the same skillet until onion is translucent, about 5 minutes. Add spinach; season with salt and pepper and cook until wilted, 3 to 5 minutes.

Beat eggs in a bowl until foamy. Add bacon and spinach mixture and stir well. Pour mixture into the baking dish.

Bake in the preheated oven until top and sides are golden brown, 35 to 40 minutes.