You don't need any expensive products to clean your acrylic tub. The first step is to wipe down the surfaces of the bathtub with a wet sponge. Once it is wet, then you can sprinkle a tub of baking powder over the bath and let it sit there for a few minutes. You can then use a sponge with some mild detergent and start working the solution into the acrylic, and it should start to form a paste. Around the drain and overflow, you can use a soft brush to clean any stubborn spots. Finally, rinse off the solution with warm water as you continue to scrub. Once you have got rid of the solution, you should be left with a stain-free bathtub.