Gravel driveways can be a haven for weeds, but you don’t need to resort to toxic chemicals. This homemade weed killer made with white vinegar, salt, and dish soap is a safe and effective way to kill weeds on gravel. Simply mix one gallon of white vinegar, one cup of salt, and one tablespoon of dish soap in a spray bottle and apply it directly to the weeds. The dish soap helps the vinegar and salt stick to the weeds, killing them quickly and effectively.