For tiny sugar ants, this works great:  Mix about 2 tablespoons of jelly with 1/2 tsp Borox (laundry additive) and put it in their path.  Day 1 you'll see about a million ants eating from it, the next day maybe a dozen or so, the next day zero.  Borox kills them and the jelly attracts them, so they eat it, they tell all their friends where to find it and they take some back in their "community stomach" for the queen and nest workers and it kills everyone.  
It doesn't just block their entrance into the house or kill just the workers (like sprays).  It kills the whole ant colony and thats the only thing that will keep them gone.