100ml of cinnamon flavored premixed ejuice, came from the company who sold it in #1 PET. Also 4oz TFA cinnamon flavor purchased from online vape shop, also in #1 PET (not purchased direct from TFA, guess the shop buys in bulk and repackages.) A bit concerning, especially with cinnamon.........However no way to know how long they were in those #1 bottles before I purchased them.
#1 (PET and/or PETE) bottles
are fine for 1-time use. You just don't want to reuse those bottles once you've used up the original contents that came in them. Many flavoring manufacturers and rebottlers use #1 bottles. They're less expensive than the #2, #4, or #5.
I will say though, that it's sort of unusual for a vendor to sell finished eliquids in them, from
my experience. Most usually use the PP or LDPE for that, mainly because they're easier to squeeze and dispense the eliquid. Those 2 are also a thicker plastic though, which is better, since they'll be repeatedly squeezed until empty.
Have some older liquids (flavors/juices) in plastic (the bottles they came in), those not even marked. Am going to toss those.
I wouldn't toss them just because the bottles aren't marked. I would though, if
the liquid itself has gone "wonky" because of extended age, which some will do. Even if they're #1 bottles, as long as the contents were originally in those bottles, the
bottles themselves haven't harmed what's inside them.