If the manufacturer of the bottle is known, the manufacturer's website can be checked to see if BPA is used by seeing what kind of plastic is used in the bottles. Polycarbonate is the most common BPA-containing material that is used to make bottles, but some companies use Tritan, which is BPA-free.
Check the bottom of the bottle for the recycling code. This is the number in the center of the triangular recycling symbol. This number details what kind of plastic the manufacturer used. Numbers one, two, four and five are safe to use and do not contain BPA. Number seven is a general category and does include polycarbonate, so it may contain BPA. However, Tritan also fits into this category.
When checking the manufacturer's website, make sure you know the age of the bottle. Although many prominent companies, such as Nalgene and Camelbak, use Tritan as of 2015, their older bottles were made from polycarbonate. It may be safer to replace older bottles to be sure of the BPA content.
Glass bottles do not contain BPA, so they can be a good choice despite the risk of breakage. Stainless steel water bottles are also often a good choice, but check the interior, because some are lined with dangerous materials. If the interior of the bottle has a golden or orange color, it may contain BPA. If it is white, it probably does not. Epoxy-lined bottles also often contain BPA.