Got Weeds? Use Vinegar: Homemade Weed Killer 1 gallon of white vinegar 1/2 cup salt Liquid dish soap (any brand) Empty spray bottle Put salt in the empty spray bottle and fill it the rest of the way up with white vinegar. Add a squirt of liquid dish soap. This solution works best if you use it on a hot day. Spray it on the weeds in the morning, and as it heats up it will do its work.