The Prophet Muhammad (sa) said: “Whoever ate a food and then said (the following du’aa) is forgive for his past [and future*] sins:
Alhamdulilla hila thee at’amanee hathaa, wa ra za qa nee he, min ghayree hawlin minee wa laa quwwah
All praise is for Allaah who fed me this and provided it for me without any might nor power from myself.
[Ibn Majah, Abu Dawud, at-Tirmidhi, an-Nasa’i. * Related by Abu Dawud. Shaykh Al-Albani declared it Hasan.]