My #1 tip for canker sores or mouth sores is to use L-Lysine(can be found at most natural food stores, vitamin shops & some drug stores) mix 1tsp in warm water, gargle and swallow. It's not the best taste in the world but it works wonders. Top 9 Home Remedies for Mouth Ulcers..
Seriously, forget about all of these! Instead, get some Lemon Balm (Sweet Melissa) liquid extract and put one drop on the sore. In most cases, it'll be nearly gone by the next day. Works on children too.