An interview is an opportunity for both of you to decide if it's a good fit. Unfortunately the seeker is usually happy to accept anything. Lying is counter productive. They only want to hear any reason that you picked their workplace. Consider it structured small talk and focus on your energy.
I generally say: "let's be realistic, I'm not passionate about what your company does. I am here to trade my time for wages and I have heard good ones about [company name].
Elaborate by mentioning something from their website to appear engaged and interested. Say you were a perfect fit because you meet all the requirements, talk about a friend who works there, mention using their products or services, or just mention that it's close to your house and will be a short commute. Ultimately this is a soft question that is just to get a quick idea of each person applying.