Building on what psychometry said, do your research. I don’t have a dev job, but I have nailed many interviews and gotten jobs after being asked this question. Read every tab on their website. Check out their linked in. If they have a blog read a few articles. Make sure this is in fact a place you want to work, and then ask yourself why you want to work there. Is it their culture? Their values? Think about what actually appeals to you about the place, and answer honestly.
After that, be sure to follow up with why you will be a good fit with with the company based on those aspects.
Lastly, if you think you can’t answer that question honestly to a recruiter, then maybe the place isn’t a good fit, and that’s ok. You can keep looking. After all, you’re gonna want to work at a place where you enjoy being.