Most paint you will find on water bottles are made from enduring acrylic, paint that is resin-based, free from any lead & other toxic substances or chemicals and authorized to be used for food. Since safety comes foremost. It might happen that with some time of usage, paint on the water flask may begin to scratch.
But careful use & washing will clearly avoid an occurrence of this issue. In case the flask is dropped, it is likely to have a dent, however, this should not cause any alarm with regards to the safety of the flask. Even in a dented condition the stainless steel flask/bottle will still serve well for quite some time ( amazing durability), without any leaching of any toxins or chemicals into your beverage.
Never the less with plastic bottles, we have a case that is a little bit different, a scratch or a fall won’t be able to cause much harm to the bottle. That is one of the reasons they are most preferred by many. Anyway, at the end of the day, the best sports water bottles should offer everything you want and need. If you want scratch resistant, you can certainly get that.