Evian dreamed up a creative way to sell even more of its bottled mineral water: by repackaging and marketing it as a revitalizing spray for your face. A 5 oz. bottle of the mineral water mist sells for $10 on sephora.com, which touts the product as a way to rehydrate and invigorate tired skin. Other brands say their water sprays will moisturize skin and combat fatigue. But the pricey bottles probably aren't that much better for your skin than putting regular tap water in a spray bottle, or just washing your face, says New York-based dermatologist Dr. Jennifer Levine.

Water sprays are useful mostly to refresh skin after a long, dry plane ride, or to reset makeup at work. But in most cities the tap water is clean enough to use as a substitute, Levine says. And water is only useful as a temporary hydrator: "When water evaporates, it could also take things [like natural protective oils] away from the skin at the same time."

Levine says she can think of only one clear benefit of using the branded spray bottle. "If the water has a nice smell to it, you might be able to use it as aromatherapy," she says. But she thinks there are more prudent skin-care choices to be made. "I certainly would rather people spent money on something like sunscreen or a moisturizer, which would at least keep the skin in better condition," she says. "I don't think [water spray] is a good bang for your buck."