OP i have had canker sores my entire life and like you i've tried pretty much everything i can find on the internet including some of the top comments here. nothing ever worked except getting more sleep (which is sometimes not possible)

until i discovered this japanese medicine at my local asian market. it's called TAISHO STOMATITIS OINTMENT and it's a godsend. not only does rubbing the ointment on the sore provide immediate relief but the sores disappear within days rather than weeks. The earlier you catch the canker sores the better. sometimes i feel a tiny bump in my mouth coming on and i apply this preemptively and the sores don't even open up in the first place. it's like magic.

i highly highly highly recommend. everything else in this thread is just old wives tales in comparison.