Sam decides to take up running, so he buys a sporty hoodie and some track pants. The hoodie is grey with reflective stripes running up the arms and white stripes on the shoulders. It’s got a little diamond shaped logo on the left breast. The track pants are standard track pants.
This outfit actually first appears in Changing Channels (5x08), when Sam wears it during the commercial he appears in for herpes medication.
Sam wears this outfit at the beginning of Shut-Up, Dr. Phil (8x05), when he comes in from his run and tries to get Dean to tell him what’s wrong.
In Inside Man (10x17), he wears the track pants (or is sleeping in them) when Dean’s nightmare wakes Sam up at the beginning of the episode and he runs to Dean’s room to investigate.
In Just My Imagination (11x08), Sam once again wears the track pants to bed, as we see him wearing them at the beginning of the episode when he wakes up and encounters Sully in the kitchen.