PET (polyethylene terephthalate) is clear plastic commonly used for beverage bottles and can be marked with any CO2 laser. Being a thermoplastic PET usually melts slightly when put under the laser resulting in a white semi-transparent mark which is a bit raised above the surface. The mentioned beverage bottles (or their caps for that matter) usually get simple expiration dates. At the same time, more intricate designs such as logos can be applied as well.