Lightly steam the spinach, tomatoes, and bell pepper. I thaw the frozen spinach in the microwave, cooking it for 4 minutes.
Mix in the diced garlic or garlic powder. Set mixture aside.
In a blender, whiz the water, flour, juice, sage, and salt. If using fresh sage, cut the leaves into small pieces before adding to the blender. Process until smooth and creamy. Add additional water, if needed.
Pour the batter into a mixing bowl, then stir in the vegetables.
Spoon the quiche batter into silicone baking cups or a non-stick muffin pan. Bake in a preheated 400-degree oven for 30-35 minutes. The mini quiches will be done when a toothpick inserted in the center comes out clean. The tops should also be a golden brown.
Allow the mini quiches to cool thoroughly before removing them from their baking containers.