Sanji is flown to Kamabakka Island by Kuma, an island where men dress like women and behave femininely like women

{Your name is Ivanna}, daughter of Queen Okama (Ivankov),Ivankov is a character that is described as a man and has the ability to turn into a woman.

On the island of the Okama, Sanji is defeated by Queen Okama's deputy, and ends up dressing like a woman and being feminine

but after seeing you Sanji found his manhood back and started to dress and behave like any other man