Add remaining 2 tbsp of oil to a large skillet over medium heat. Add onion and sauté for 2 minutes until starting to soften. Stir in garlic and continue to cook for 2 minutes, stirring often. Add spinach and toss until wilted. Stir in tomatoes, sugar and salt, stirring to combine. Simmer uncovered for 20 minutes until 3/4 of the liquid has evaporated. Remove from heat and stir in fresh parsley, basil and bread cubes.