If you go with the bowl in a bowl idea, put a little bit of dish soap in the water to break the surface tension. otherwise the ants will walk right accross it!
I am a HUGE fan of Avon Skin So Soft Bath Oil. (Original scent. I know many people don't like the smell, but it's SO much better than bug spray!) when I had cats and ants, I would put a little ring of it around the bottom of the bowl, and the ants would stay away. I also used to soak a cotton ball with it and place it where the ants came in. Then they wouldn't come in. Sure, I had cotton balls all over, but that was better than ants! and non toxic too! And very affordable! hooray! After awhile, I didn't have ants anymore. previously? my apartment was absolutely infested.