Sorry' I gave such a short answer. Cleaning is a good idea, you don't know what has been crawling around them or what chemicals, a nd nasties they have been exposed to. Now you might be thinking that is why I'll sanitize, but if there is a pesticide or oily residue for some reason you don't want that in your beer. Do you have to scrub them with a bottle brush like bottles that sat in a dank corner of a frat house? No. Maybe use some one step cleaner shake up a good bit the sanitize before filling. You'll get all the dust and stufff out. But hey it's your beer, and it's your call.