The primary difference between coffee cake and regular cake is in their intended consumption and topping. Coffee cake is characterized by a crumbly streusel topping and may include ingredients like cinnamon or nuts. As the name suggests, coffee cake is designed to pair well with coffee or tea and tends to be less sweet and is suitable for breakfast or as a casual snack. In contrast, regular cake can encompass a wide range of flavors, textures, and sweetness levels, and it is typically served as a dessert for special occasions.