A.M.
See if he'll drink from a straw. My youngest niece hated using sippy cups so my mom tried her on a straw and she loves it- and does very well. At first, she used the ones that the straw part is soft plastic/rubber and you have to bite down on it a bit to get the liquid flowing and it also goes into the lid part so it isn't always sticking out. Sorry, I don't remember the name but I got them at Meijer or Target and they still sell them in a 1 or 2 pack. Now she'll drink from any type of straw with no problem. Good Luck!