Trying to nail jello to a wall.

That would be difficult since all I could ever offer is to wait until the child is ready, however in your child's case I have no clue.  If it were me I'd seek adivce from the peditrician.  

Does your son see a psychiatrist?  If so he/she might be able to give you some tips on how to potty train him with these disorders.

No. Psychiatrist are for people needing medications for mental health related issues. My son has seen a psychologist, but she felt he was too young for individual therapy, but assisted me in getting him involved in several early intervention programs. I do meet with her on occassion for parent consultations.

Quoting TylersMom999:

Does your son see a psychiatrist?  If so he/she might be able to give you some tips on how to potty train him with these disorders.

I would talk with those in the early intervention programs.  With his sensory issues does he even know when he has to go?  Then I would find some little reward that he likes and give it to him every time.  Make it a case of if yuo want the mm's you use the potty.  This way it's his choice and not a battle with him. If you push the more he will fight you.  For the person who asked ODD is oppositional definate disorder. 

Do you have a step-in shower (as in not a shower/tub)?  We trained ours by starting in the shower (during the evening, right before actually getting in the shower).  That way it doesn't matter if it sprays everywhere because it's an easy clean-up for both the shower and the kiddo.  They can also practice aim by pointing at the drain.  Neither of ours have a sensory disorder, but our youngest is showing all the signs of ODD (but is too young to receive an actual diagnosis) and this method, though slow going, has worked well.

A note of warning... if he's like ours, he might insist on peeing in the shower for a while.  I don't have a problem with it because I can just spray it down the drain when he's finished, but it does make it interesting when you have to go out (or to school).  It took almost a year before ours would opt for the potty over the shower (and even now while he's home he would still prefer the shower), but he was fine if there were urinals because it was similar to the shower.

ODD is oppositional defiance disorder

Mine can't go at all on a potty ever.

Quoting TeaHound:

IDK. My first ds wasnt potty trained until 4 and my younger one is 3 and not done yet. (Lots of puddles and/or reminding).
I don't know what ODD means, but the pediatrician advice thing sounds good.

I've actually tried that. He's terrified he'll get dirty and he don't want to make "his tub" dirty.

Quoting trebelcleff:

Do you have a step-in shower (as in not a shower/tub)?  We trained ours by starting in the shower (during the evening, right before actually getting in the shower).  That way it doesn't matter if it sprays everywhere because it's an easy clean-up for both the shower and the kiddo.  They can also practice aim by pointing at the drain.  Neither of ours have a sensory disorder, but our youngest is showing all the signs of ODD (but is too young to receive an actual diagnosis) and this method, though slow going, has worked well.

A note of warning... if he's like ours, he might insist on peeing in the shower for a while.  I don't have a problem with it because I can just spray it down the drain when he's finished, but it does make it interesting when you have to go out (or to school).  It took almost a year before ours would opt for the potty over the shower (and even now while he's home he would still prefer the shower), but he was fine if there were urinals because it was similar to the shower.

I honestly can't tell if he knows when he has to go. Sometimes he acts like he does, others there is no way he knows he has to go. Rewards/bribery to potty on the potty don't work. Tried it. He's never even been able to go in the potty. 

Quoting mommy2boys03:

I would talk with those in the early intervention programs.  With his sensory issues does he even know when he has to go?  Then I would find some little reward that he likes and give it to him every time.  Make it a case of if yuo want the mm's you use the potty.  This way it's his choice and not a battle with him. If you push the more he will fight you.  For the person who asked ODD is oppositional definate disorder. 

Have you tried getting a kids urinal?  I think they're absolutely disgusting (lol) but if it works, it works.  It sounds like you've tried just about everything you can.  The only other recommendation is instead of expecting him to know when he has to go is to tell him he needs to go.  It's a challenge (especially with ODD), so getting a watch with a timer (or even better letting HIM pick a watch with a timer) and setting it to go off each hour for "potty" time is the best I can offer.  My youngest had a problem identifying the urge to go (and still does)... constant reminders are one way of preventing accidents.  Also, try breaking it up into daytime, night-time, pee, and poop.  Work on one at a time (daytime pee is easiest for us, though daytime poop is easier for others) and focus on the times he does go while using encouraging words for times he tries to go but nothing happens.  The reward we used for both of ours was giving them the priviledge to flush (LOL), but I'm not sure if that would work given his sensory disorder.  Just keep on trying... some kids just take longer than others!!!!