Nearly nothing works. It's not completely understood how labour begins but research has never found a link between pineapple and sex and similar theoretical natural methods and labour. In fact, some of the research shows, for example, that sex might prevent labour happening soon. Of course people do all of the old wives tales and then go into labour. But hundreds don't. It's just coincidence. People also eat biscuits, watch Love Island and pick their nose just before labour starts. But we don't quote them as linked.
Because we don't understand the process really (it seems to be the baby that decides the process in communication with the woman's body), people take a theory and run with it. Like an enzyme in pineapple is linked to labour, but actually you'd need to eat 8 pineapples, leaves and skin included, in one sitting to replicate it. And even then, it probably wouldn't work. And the prostaglandins in semen, are also linked to the induction process BUT the type of prostaglandin would need to be ingested orally to replicate the process and again, research shows no link.
Raspberry leaf, as others have said, was never recommended to induce labour, but to make it more effective in the later stages. I'm not sure how but during my time on MN, it's been erroneously linked with labour induction.