While it may be tempting to simply pour expired or unused colognes down the drain, you should never do this, for fear of contaminating waterways in the drainage system. It's always a better idea to contact your local hazardous waste facility and ask about the proper way to dispose of cologne in your municipality. The bottles, however, are typically made of glass or plastic. This means that they can be recycled once emptied in your regular blue bin, though you may want to remove the spray mechanism or cap of the cologne bottle.