S.D.
To clean sweat stains on clothes,what I use is a liquid named lestoil,you can find it on a Kowalskis Store, on the cleaners area ,it is like yellow oil and have a strong smell, what I do is put some of the oil on the stain and let it stay for a couple minutes then scrub gently , if the stain is still there do it again using more, then once the stain is gone rinse well then wash it like always, it works very good, however, I suggest you try it on an old shirt first