Coming from the beverage industry, I can answer this question.

Canned water is in fact sold, although in very small quantities. Typically more sparkling waters go into cans than still waters. La Croix is probably the largest brand available in cans. Dasani did sell some canned still water, and some small brands still do. Still water used to be put into cans for vending machines and for airlines, but small bottles have now been designed to fit into can vending machines.

A key aspect of water packaging is to emphasize the clarity of the product (showing its purity , etc.). Aluminum cans obviously do not allow a person to see the clarity of the product. In addition, there is a sensory perception associated with the aluminum can: when people drink out of an aluminum can, they expect what hits their mouth to be carbonated. This is from years and years of drinking soda and/or beer out of cans. Try drinking plain water from a can; it feels a bit strange.

There is not a flavor issue. Every aluminum can's inside and lid is coated with a plastic lacquer (generally epoxy-based). These are tested extensively and will maintain a shelf-life well beyond that of a plastic bottle. If cans weren't coated, the aluminum would oxidize, and the can would leak. The only bare aluminum that could come in contact with the product is along the line where the can is opened. Any metallic taste would have to come from this; although smelling the bare aluminum of the tab may also be a factor.

Cost is not the issue; the aluminum can is cheaper to make than a plastic (PET) bottle. This is why your PBR or Natty Light is usually in a can; cheap beer goes in the cheapest package. Aluminum cans are made at speeds and scales that can blow away anything plastic bottles can do. PET resins used for plastic expensive as well.


Credit : yahoo answer