have you tried water from a water bottle? maybe with a kala cup top on it? E is a good water drinker, but given the option of her sipper cup or MY water bottle, she chooses my water all the time - we have started putting the tops from her kala drink cups on a bottle of water and she is all over it...

if you're concerned about keeping his fluids up, can you feed him extra fruit for the fluids in it?

as to introducing cows milk, i have NFI on that one sorry hun!