Name: Dad
Comments: My teenage son on the spectrum seems to do everything without any effort as though he is never interested. I love him a lot but I just want him to achieve things. This goes for school work, eating just anything at all. How can I get him to do things as though he wants to accomplish something and progress?
It could be low self esteem / depression. Now, this is not a judgemental question more for you to reflect as I had to: How much times per day to you build him up about the good things he is doing? Many on the spectrum may already feel inadequate (Even if not expressed) and need to feel that they are good at something. I did notice you did not mention him being oppositional or aggressive so that is a good thing.
Some people with Autism may see even tasks that neurotypicals think as small as bothersome or as not worth the effort. Depending on the mental/emotional state of your son, he may be feeling too depressed or not motivated to take care of himself. It may be a wise idea to seek out professional counseling for him.