Adding Vinegar to the Wash Cycle
It may seem counterintuitive, but adding a splash of vinegar to your wash cycle can remove the "oops I forgot I was doing laundry" smell from those clothes that sat too long in the washing machine.
I have been guilty of this a few times, and tried the vinegar method after seeing it on Pinterest. I literally added between 1/4 and 1/3 cup of vinegar (I eyeballed it) to my wash cycle in addition to my normal laundry detergent. I can attest - the clothes come out smelling CLEAN! Absolutely no smell of mildew OR vinegar!