Pineapples and pineapple juice thin the cervix
Unfortunately, nothing works until your body is ready. The best way to encourage your body is to relax. During labor, your body produces a hormone called oxytocin. That hormone is also produced when relaxing, having sex, laughing, hugging, spending time with people you care about and feeling loved. Getting babies things ready, a warm bath, a pedicure or massage, feeling love from your partner, family game night will all encourage the production of oxytocin.
Trying every old wives tale in the book will only frustrate you and stress you out. Those feelings inhibit the production of oxytocin.
No, pineapples do nothing for labor. That's purely a myth. There is an enzyme in pineapples that some people think my help progress labor, but you'd need to eat 7-10 whole pineapples, to include the skin and core.
Sex and your partner's semen. It softens the cervix.