How can i get my child to drink?

My 3 year old was in hospital with swelling in the brain during this time he stopped walking talking and eating and drinking..He has since recovered and is back on his feet..But the only problem is he won't drink he is receiving fluids through a ng tube but we have been told to encourage him to drink I have done everything to coax him to drink but he still refuses when I ask him to drink he points to the tube I think he knows he is getting his intake from there .I can't get the tube removed as he is on loads on meds which go down his tube Im worried he will never drink again..Ive bought every cup bottle etc he is also on the autism spectrum so we have been told this is behaviour issue..Anyone any ideas on how I can get him to drink I'm all out of ideas