What is the ruling on a sane, adult man who does not fast? And what is his punishment in this world?

Intentionally breaking the fast of Ramadan is a major sin, necessitating repentance and making up the missed day. Whoever considers breaking the fast permissible has committed an act of disbelief (kufr), and whoever openly breaks it shall be punished. Al-Nasa'i narrated a hadith describing the punishment of those who intentionally break their fast before the time of iftar, stating that they will be hung by their hamstrings and the corners of their mouths will be torn.