Weed killers contain chemicals that are dangerous to pets and potentially to the water supply. Either bleach or vinegar can kill weeds but they also have their disadvantages.
Vinegar and bleach both kill weeds. The acidity of vinegar destroys weeds. Bleach contains surfactants, compounds that help it penetrate weeds and damage them so badly that they are killed. Either liquid can be poured at the base of weeds. However, more than one application could be needed.
Bleach and vinegar will not just kill weeds; they can also kill grass and other desired plants nearby. Bleach is dangerous for pets or children who could play in your yard. If you wish to kill weeds over a large patch of ground, using bleach will damage your soil so that it will be difficult to grow anything else in the treated area.
If you only need to kill a few weeds, pour vinegar on the roots every three days until the weeds die. Keep bleach use to inside the home. Never combine bleach and vinegar; doing so can create toxic fumes.