According to Serious Eats, the most prominent flavors in a cream soda should be vanilla and cream. These flavors can be artificial or natural, but should always be present in "balanced proportions."
Old recipes of cream soda included egg whites and lemon oil to produce a creamier texture, while modern recipes focus on a typical refreshing soda texture. Carbonated water and cane sugar or high fructose corn syrup are now the major ingredients in cream sodas of nearly all brands. Artificial coloring is often added to produce a golden-brown appearance in modern sodas, while older cream sodas lacked this artificial coloring.