Smoking tobacco is Haram (prohibited) for it causes great harm and has no benefit at all. Whoever smokes should give it up and repent of it. As for your father, you should advise him. Concerning giving him a drug that makes him ill for two days in order to give up smoking, this is not permissible without his knowledge. Allah knows best.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.