The best cleaning products for removing stains from bathtubs are natural products like baking soda, vinegar and cream of tartar. Oven cleaner and shampoo are also effective for bathtub cleaning.
Baking soda cleans many areas of the home, including the bathtub. Combine it with hydrogen peroxide to make a paste. Apply the paste over stains for about an hour, then scrub the stains clean and rinse. Alternatively, a baking soda and vineger paste is also effective. In the absence of baking soda, cream of tartar and hydrogen peroxide paste make a sufficient substitute.
Shampoo is often the easiest product to use since it is already in the bathtub or shower. Pour shampoo over the stain, let it sit for several minutes, then scrub away the stain. Oven cleaner is best for a white porcelain tub.