Boiling water, vinegar, salt, sugar and corn meal are all products that can be used as pet-friendly weed killers. In addition, many garden centers offer organic and pet-friendly weed and grass killers that can be used in a garden without fear of making pets sick.
Boiling water, vinegar, salt, sugar and corn meal can all be poured at the base of the weeds to be killed. Care must be taken with boiling water, which kills all plants it contacts, not just weeds. Salt is best used as a weed killer in an area where no plants are wanted, such as a patio, since it makes the soil unsuitable for growing anything.