Coca-Cola plans to take a piece of the £2.4 billion sterling a year US bottled water market by selling its own brand of purified water next year. The soft-drink giant, which has sold mostly sugar water for the last 112 years, will introduce plain water in plastic bottles in selected markets early in 1999 and across the United States later. Pepsi Cola entered the water business in 1994. The leader in the US bottled-water market is Perrier.