Try Baking Soda and Water Add about one ounce of baking soda to a freshly washed plastic baby bottle, and fill the rest of the way with hot water. Cover the top, and shake the bottle until the baking soda dissolves. Allow it to work to get rid of the smell of sour milk for several hours or overnight. Rinse away the baking soda, and wash and rinse the bottle as usual. http://voices.yahoo.com/how-rid-sour-smell-milk-plastic-5083175.html?cat=25
Depending on where you live and work, you're likely to be exposed to many plastic products every day. Food and beverage containers, some disposable plates, and toiletry bottles are all plastic and all are made from chemicals. Research suggests that all plastics may leach chemicals if they're scratched or heated. Research also strongly suggests that at certain exposure levels, some of the chemicals in these products, such as bisphenol A (BPA), may cause cancer in people.