Your step-sister's friend is back from the gym, wearing her sliders to air them out, and tells you how this girl kept looking at her because her feet were stinking up the entire locker room. She knows you like it though. She pulls her own feet up to her face to smell how bad they stink, and then sucks on her own sweaty toes...

She doesn't have any lube, so she uses just the sweat from her feet, and her spit, to give you a stinky FJ.