I have used 12oz PET bottles for 12 to 24 bottles of all my brews - to share with family and friends, so I don't have to collect glass bottles later, or for my own use - drink first, save the glass bottles for later.
I got lots of grandkids that drink sodas - I have an unlimited supply. But had to convince them to get the 12oz bottles. Lately, there have been sells on this size, generally $10 or less for 3 8-packs (24 bottles), almost cheap enough to just buy and dump the soda.
One of the nice things about these PET bottles is that you can fill to proper level, then squeeze the bottle until the liquid level is at the top of the neck, and quickly screw the cap on. This eliminates air in the bottle, and you know it's carbonated when the dent goes away, and the bottle is very firm when squeezed.
Yes, they're easy to sanitize. I rinse with tap water, rack to dry until ready to use. On bottling day, I dip both bottle & cap in Star San, shake off, then fill.
I've never noticed any carryover flavors, from cola, 7up, DrPepper, orange or any common sodas. It's been warned never to use a ROOT BEER bottle, as the taste/smell never goes away. But, I have bottled a few heavy beers (strong ale, stout, DIPA, etc) and really didn't detect any carryover smell/taste, but I don't have much of a discriminating palate.
I've never had a PET bottle cap leak, or lose carbonation, but I screw them tightly when filling, then, later, tighten again using a paper towel or rag for better grip. This has backfired a few times - having to use a pair of pliars to loosen the caps, to drink.
and yes, store them in a box or dark closet - don't want them getting 'skunky'. Note: a case of 24 - 12oz PET bottles fit nicely in a 5-gallon bucket, using a piece of cardboard as a shelf for the 2nd level.
Strip the label from the PET bottle - you'll never get it all off, and I've never found anything to remove the spot of label adhesive. And address labels are great and cheap for simple identifiers of what is inside. Or, just write on the bottle with a permanent magic marker.
yeah, I know, it looks really tacky -- Shut up and drink the beer, it's homebrew.