How do you motivate those employees, in giving out their best, who don't want to work for incentives?

Simple use a red apple theory Show them a goal if you achieve your target who knows with salary increment you can get promotion in bonus

Some times recognition among team meeting . giving them additional responsibility or assignments as reward

appreciation of their work motivate by some incentives

Thank you for your great effort on this project.
Your performance this month was very impressive. We always hope for more from you.
I would be very interested to know your opinion on this matter and what is the most appropriate decision to make.
My goal is your development at work because the company’s success is due to your success.
The success of this project would not have happened without your efforts.
If you encounter a problem while working and want help, do not hesitate to contact me.
I strongly believe in your abilities and skills, and I am confident that you are able to achieve the expected success.

you give them unexpected gift

Attainable target, maybe they don't want to do extra effort its because unbelievable to reach it. They don’t want to try and waste their effort in the end they didn’t reach it

The easiest way to increase employee motivation is to emphasize open, positive communication at work. And we don't just mean sending emails of thanks and encouragement, but making sure you talk to employees in person as much as possible.