I like using thing i already have at home to do things it less expensive and this recipe is safer for the environment, i found this recipe in one of my favorite gardening books Garden Any were by Alys Fowler
All you need is:
4 Cups of vinegar Half a cup of Salt A couple Tbsp's of dish soap
Once the salt is completely dissolved you can either spray or wipe it on the leave of the weeds, now be careful can be deadly to surrounding plants. It also works best in sunny conditions.