Weird smelling water bottles

Hey guys I was just wondering if any of yall have been having this issue, whenever I purchase either sams club brand water bottles or ozarka water bottles they smell like absolute s**t when you first open it. Im talking about how its still sealed and everything and upon unsealing it you get a fat wiff of either mold or something, but after the initial unsealing the water tastes normal and the smell goes away, anyone else having these issues? Does anyone know why?