I had researched this in recent past because we had a problem last year with ants in our kitchen and bathroom, and it was shortly after renovations. We got an exterminator because we needed immediate help. They applied bait which supposedly is taken back to nest.
However, if there are just a few ants here and there and you need a quick natural fix, you can spray with a vinegar and water mix because ants do not like vinegar so they will stay away. However then I was told that the vinegar was bad for my granite countertops, so instead alcohol in a spray bottle will do the trick. Alcohol is OK on granite and will clean your countertops and will also kill the ants.