How can you remove rust stains from Acrylic bathtubs?

A fresh stain will be easier to remove than an older, set-in stain. Your first step should be to find and remove the source of the rust. You don't want your problem returning. As with all stain...

if the clothing is a light color, it can usually come out by soaking the clothing with lemon juice and then rubbing in some sea salt on the stain

call a specialist, maybe try bleach, or just keep those things dry after they have been wettened

CLR (Calcium, Lime Rust) Remover.

You have to use some of your coke at home. Before you sleep, pour some of your coke on the stain and you can also add some bleach and let it be there overnight and rinse it off the next day.