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BIFL – BPA free thermos(r/BuyItForLife)
Be aware that BPA-free plastics often contain other endocrine disrupters, sometimes even worse than BPA. Your best bet is to go with one that is uncoated metal (I believe many of them coat the inside with plastic to prevent the metal from reacting with the contents and producing an odd taste).
That being said, since the “what’s the best insulated mug” question comes up on BIFL about every 13.6 minutes in average, I can confidently tell you the answer is Zojirushi. www.amazon.com/Zojirushi-SM-KHE48AG-Stainless-Stee…
One reviewer claims it is uncoated.