When we taste-tested 39 bottled waters, we found that the major differences were due to the type of plastic in the water's bottle. There's no single answer. Small amounts of chemicals in the plastic itself could leach into the water. Even the process used in making the plastic could affect taste. The temperature at which water is served can also affect taste.
Differences are most obvious when water is at room temperature.
When the water is ice cold, differences will be less noticeable.