Gain Interview experience

I am a software developer with 5 years of experience. I am looking to gain some interview experience and also see if I meet market requirements and I am demandable.

I want to know if it is really fine to apply for a job role, get interviewed and if we get selected then we deny the offer.

I have seen some professionals do this just to see if they are competent and if they meet market requirements.

But doing so will this create a negative impression among the employers?

What reason can we give if we want to deny the offer?