How can sexual fantasies and feelings resulting from sorcery be treated?

Your question is unclear, but generally, one should not rush to attribute problems to touch (mas) or magic (sihr). Instead, one should consider the apparent causes and treat them with legitimate means. As Sheikh Ibn Uthaymeen said: "How often does a person fall ill due to delusions that generate in his heart until they develop and become a reality. If a person becomes heedless of something, turns away from it, and distracts himself from it, then it will disappear by the grace of Allah." To get rid of sexual fantasies, you can refer to Fatwa no. 160587. Marriage is the best cure for this, along with consulting a psychiatrist, maintaining regular recitation of adhkar (remembrances) and ruqya (incantations), and relying on Allah.