I once head to try to remove the smell of smoke from some beats pros headphones I bought for a friend. It was a long process that took several days, and I still never fully got rid of the smell.
Most of the smell gets soaked into the pads and headband, so best possible solution would be to completely replace the pads. Over the course of those several days where I tried to remove the smell, I tried everything from soaking in detergent, oxiclean, baking soda. The thing that worked better than everything else was letting it bake in the sun for extended hours on end. The sun's UV does a decent job at breaking down the smell, but I still never fully got rid of it.