Crumble sausage into medium skillet. Cook over medium heat until browned, stirring occasionally. Drain off any drippings; set aside. Bring water to a rapid boil in large saucepan. While stirring, add grits in steady stream until mixture thickens into smooth paste. Reduce heat to low; simmer 5 to 7 minutes, stirring frequently to prevent sticking. Stir in sausage, spinach, cheese and tomatoes. Pour into greased 9×5-inch loaf pan. Refrigerate until cool and firm.
Unmold. Slice into 1/2-inch-thick slices. Heat oil in large skillet over medium-high heat until hot. Add garlic; cook and stir 30 seconds or until soft. Add grit slices, 4 to 5 at a time, and cook until golden brown on both sides. Repeat until all slices are cooked. Serve hot. Refrigerate leftovers.
Serving Suggestion: Melt thin slice of mozzarella cheese on top of each browned slice. This also makes a wonderful side dish for chicken, topped with warmed seasoned tomato or spaghetti sauce.