My son (almost five) seems to have no interest in drinking anything and every day it is a ridiculous battle to get him to have even a few sips. The result is that he is regularly very dehydrated, which is obviously very unhealthy and also affects his behaviour. He has no shortage of energy and is generally very robust and well, but when he's dehydrated he gets very naughty, and also constipated. I am at my wits end with it - he will go 12 hours through the night without anything, and then not even want a drink before going to school in the morning. During the school day, I suspect he barely drinks anything at all.Has anyone had similar experiences? Any advice/tips? It doesn't seem that he dislikes the taste of drink (he hates fizzy drinks/cola etc) and I am happy to give him juice/Ribena rather than water/milk if that gets something down him - it's more that he has no interest in drinking. Is this a doctor case?