Apple Cider Vinegar isn’t an Effective Remedy for Killing Ants
No, apple cider vinegar doesn’t kill ants, even if directly applied on top of them. The use of apple cider vinegar against ants comes from the fact that it can throw off their sense of smell from the pheromones they usually release and follow to food sources.
Ants will nest in areas with a food source, usually forming a long line from their nest directly to the food source. They do this by releasing pheromones on their way back to the nest after getting food, allowing other ants to follow it back to the source and grab more. When apple cider vinegar is applied along this line, it breaks off their sense of direction to the food source and back to their nest, leaving them aimless.
The best way to do this is by mixing equal parts of apple cider vinegar with water in any amounts you see fit for the situation, then pouring it into a spray bottle. After you spot the ant line, spray along the line. Get rid of their food source while they lose the scent from it to avoid them from coming back to it later.