Toomas, My chameleon is having a similar problem. My vet said if the chameleon is drinking more than usual he could have a problem with his kidneys. Check the urates (white part) of his droppings. If they are peach, pink or orange this is a sign of Kidney problems. Keep giving water and force feeding but not too much food at first. Try Pedialyte several times a day small amounts at a time. Give him a product called Repta-Aid the kind for insectivores not herbivores. It is made by Fluker. It makes force feeding easier. There are instructions with a chart that shows how much to give for his weight. Kidney problems can be from too much vitamins too little water or the animal was born with a weak kidney. I wish you much luck and you should keep consulting a vet, but make sure they have lots of experience with chameleons.