Does too much sugar consumption cause canker sore, or are they caused by something else?

No: Generally oral ulcerations, commonly they are aphthous ulcers, are brought on by stress or illness. Sugar is not a known trigger.

Maybe: Canker sores usually are triggered by something that you do. Sugar could be a trigger in some people. Keep track of what common things that you eat or do just before the canker sore appears. The trigger can activate a virus that displays itself as the canker sore.