In a large 6 quart slow cooker, add the potatoes, carrots, celery, onion, zucchini, green beans, broth, diced tomatoes with their juices, tomato sauce, Italian seasoning, sugar, salt, garlic powder, pepper, and bay leaves. Stir until well combined.
Add the drained and rinsed white and kidney beans. Gently stir.
Cover and cook on low for 6 to 8 hours or on high for 4 hours.
Remove the bay leaves. Add the chopped spinach leaves. Stir.
Cover and cook for an additional 15 minutes, until the spinach is soft.