I don't think it's that easy.
You can eat unhealthy diet, smoke cigarettes, and live a lifestyle that increases your chance of getting cancer and you still may not.
You might not have the genetic predisposition to get cancer through unhealthy lifestyle.
Also, I don't think it's going to happen fast anyways, might take years. Also, I don't think it's worth it. Your idea might be to avoid the discomfort/pain of the accessable methods by getting cancer and sighing up for euthanasia. However, you will probably suffer more in your way to getting cancer and up to euthanasia than if you were to go with accessible methods.
Just my own opinion though.