The laundry detergent brand Meyers makes an all purpose cleaner with a lemon verbena scent that is good at cutting smells. I've used it on a pair of workout leggings that smelled of cat urine. Worked on those, not sure if it will fade your jeans or not though.
Also, I once had a faux leather purse that reeked of fish. No matter how many washes, the smell would not come out. It was awful. What ended up doing the trick was filling a paper bag with kitty litter and leaving it in there for a day or two. The litter absorbs the smell. Kind of a funny and weird little trick, but it totally worked.
Hope this helps. Good luck!