Officials have said they excluded high-calorie milk drinks because milk provides nutritional value.

WSJ: City Drinks Plan Questioned

Things get even murkier when drinks are classified as nutritional supplements, not beverages.

FORBES: Magazine Article

But unlike food, alcoholic drinks have very little or no nutritional value.

BBC: Alcohol calories 'too often ignored'

Sierra Mist, a new caffeine-free lemon-lime soda that competes with Coca-Cola's Sprite and Cadbury Schweppes' 7up, doesn't exactly make soda into a nutritional beverage, but it blunts one long-standing criticism of Mountain Dew and cola drinks: that they use caffeine as a hook.

FORBES: Pepsi's New Challenge