Turn of cookies

If you want to turn off cookies, go to the Safari/Preferences/Privacy Preference and check Block all cookies. Doing this may cause problems when accessing some web sites.

One method is there to turn off cookies use private browsing see this article Browse in private in Safari on Mac - Apple Support

From your Safari menu bar click Safari > Preferences then select the Privacy tab then click Manage Website Data then click Remove All > Done then quit and relaunch Safari.

Enabling block cookies - but iPhone continues to accept them. When you review advanced settings and see website data there is evidence that cookies are not blocked