You have got to check these out!  I was in Bed Bath and Beyond the other day and noticed they had the cutest stainless steel water bottles that are the perfect size for kids.  The outside includes a rubbery material helps with their grip and has fun 3-D designs and over 150 popular names.  When I went to look up the company (Namesake), I discovered that they even have sippy cups for the really little ones!  Both are BPA-Free. They are also sold at Kohl's.