Well, according to the powers-that-be in New York, they are and they want them to start carrying warnings about tooth decay. But are they really that bad for your toddler?

As with most things, it all depends on what you put in the said sippy cup and how your little one drinks from it. Water will cause no problems, but exposing little baby teeth to sugary juice or milk can cause problems – especially if you give them a sippy cup filled with such delights overnight. Liquid can pool around the teeth, and cause cavities.