May (will) sound silly but to clean them, I always put my earplugs in the pocket of my trousers, and throw it in the washmachine to get rid of the earwax. They really sound better after drying.
And these are high quality earplugs.
However, headphones will probably not fit into your pockets, but if you've lost all hope and you're irritated enough to buy a new pair; if your headphones don't contain any watersoluble material like paper/carton, you can try and put them in the wasmachine, covered in a piece of cloth.