I hate Canker sore medicine. It costs soooo much.
The spray works best. There's that stuff where you have to swab the sore dry (
) and then soak a special q-tip kinda thing in this medicine that glazes over the sore and makes a water-tight seal that works pretty well. the only problem is that it hurts like a bitch to apply and, depending where the sore is, the seal can be rubbed off pretty easily with your teeth or your tongue or whatever.