I would probably soak it in a 10% bleach/water solution, just make sure to rinse it out and let it dry well. I guess I’ve never really thought about how one might go about disinfecting ropes XD At the shelter i work for, we always just toss the dog rope toys in with the laundry, which gets washed with detergent and bleach.
Submerging it in boiling water could also do the trick, depending on the materials.