Is it possible for bladder spasms to just occur with no known origin and foods not trigger it?

Yes.: Bladder spasms do have a cause, but it can often be difficult to identify. Avoiding foods on the "interstitial cystitis" list certainly can help some, but bladder muscle overactivity can have complicated neural, muscular, and inflammatory causes. Work closely with a female or neuro-urologist to continue to look for causes & to find ways to improve your symptoms. Much luck to you.