There is a Japanese-made katakana expression PET bottle, which refers to plastic bottles. More than 10 or 15 years ago, the NHK English show taught that "PET bottle" is a katakana expression and should be expressed as plastic bottles in English. These days, however, some English speakers living in Japan say PET bottle is okay. Is PET bottle used as an English expression in English-speaking countries?
PET is a standard abbreviation for a particular type of plastic, polyethylene terephthalate. It is used when sorting plastic items for recycling, but in everyday conversation I think most people would call it a 'plastic bottle'.