We bought Bailey a reflective jacket and he hated it (went ballistic when we put it off and frantically tried to get it off)
Since he responds well to clicker training we started teaching him to like it and now he actually noses it until it's over his head.
Introduce the jacket slowly, first at a distance, and click and treat for no reaction (if he reacts leave it on the counter or floor and distract him with a game or two until he gets used to it being in his presence) Jackpot treat for him looking at it with no reaction and keep on clicking whenever he makes eye contact with it and doesn't react (he doesn't have to be wagging his tail- disinterest will do fine at this stage)
Slowly move closer to the jacket, or bring the jacket closer (whichever he is more comfortable with)
The idea is to get him to like looking, and then interacting, with the jacket. So loads of treats for a paw touch or sniff or walking towards it.
Once he is comfortable enough to actively seek out interaction between the jacket and himself, start shaping him to like having it put on him (i.e. if it has to go over his head feed him treat through the neck hole of the jacket, first extending your hand through the hole so it's not so close to his face, and gradually treating further 'inside' the neck hole until he ha to stick his head through to get the treat)
This should be done in short sessions and always end with his favorite game or activity to keep things on a positive note.
As always with clicker training, remember that initially the treat has to come immediately after the click and once he i comfortable with the exercise (i.e. fully comfortable with you putting on the jacket and fastening it etc) then you can wean him off the treats, increasing the time between clicking and treating, and also rewarding with other things such as praise and toys.
It seems like a long process but goes surprisingly quickly, and we worked it into the middle of our other training sessions so he didn't get scared or overly excited by the scary jacket. We also increased the value of the treats the closer he got to the jacket, and the more he volunteered interaction. If he is not progressing as he should (he cowers away or still reacts to the jacket) it might be that you are going too fast for him or your treats aren't high value enough. Increase the distance between him and the jacket and treat often. Never end with him feeling unsure of the jacket, even if you have to go back to step 1 again (we want him comfortable with the jacket so he associates it with only good things, and the closer he gets to the jacket the better he feels)
It worked for us, so I'm sharing it with you in case you want to give it a shot. If anything is unclear just shout and I'll clarify.
Also- it might be the smell of the jacket. A blanket that we bought for Bailey smelled of the other animals at the vet shop and he only used it once we had washed it a few times.