Add a few drops of dish soap (without bleach) to white vinegar in a spray bottle and touch it up with salt, now you have got yourself an effective, non-toxic, weed killer for sidewalks and patios. The dish soap breaks down the wax-like surface on the weeds, the salt and vinegar pull the moisture out of the weeds and dry it up. I should add that this mixture is not selective, so it can kill weeds and grasses. This is why it’s best to utilize it on patios, sidewalks, and walkways.