Sippy cups should be used as a training tool from the bottle to a cup and should be discontinued by the first birthday. If your child uses a sippy cup throughout the day, fill the sippy cup with water only (except at mealtimes). By filling the sippy cup with liquids that contain sugar (including milk, fruit juice, sports drinks, etc.) and allowing a child to drink from it throughout the day, it soaks the child’s teeth in cavity causing bacteria.