When our eldest DS (severely dyslexic and on the A spectrum, not expected to do well) was doing his A levels, he came home and announced that "all" (quite a few) of his friends were getting cash rewards for results, some were ridiculous amounts, and he felt he should get the same treatment,
I agreed that I would give him a hundred pounds for each exam failed, I explained that he would need all the money he could get, if he wasn't able to open the doors that success from passing the exams would achieve.
The house rule is if you fail an exam, you get a hundred pounds, I've not had to pay out yet.
I believe and try to drum into my children, they are doing the study, training and work for their own benefit, theirs alone, the harder they work now, the easier life will be later, the best incentive, is installing a personal dive in them, they can push themselves far harder than any one else can,
Nurture the self drive in them, and you will end up worrying they are overdoing it rather than making them dig their heels in.
If you push, they push back, stop pushing.
Enabling is a far better use of energy.
Eldest got highest marks possible in all of his exams,
Adolescents get overwhelmed by the enormity of their targets in life, tell them to forget about the big picture, just keep doing all the tiny steps, next time they look up, the target will be a lot closer.