clean the sink with baking soda and vinegar......it will foam up just rinse it down with warm water from your kettle...................they do not like the vinegar........mix some white vinegar in water and spray your counter tops and under the sink......they are getting in somewhere......look around where the pipes come in you might have a tiny opening there.........use watertight caulking and spray the perimeter outside your home to keep them from coming in............if you have a basement or crawl space you might need to see the other openings and seal them. also check the bathroom area to see if there is an opening around the pipe area. Once we cut down our poplar trees this year..........no more large ants........and that was 50 ft from the house but I could see them traveling up and down the tree..................They also do not like clorox-cleanup but I have to put an exhaust fan on when using that. I do the wood with an orange cleaner...do also do not like that..........