1. Before you start fasting
Wa bisawmi ghadinn nawaiytu min shahri ramadan
I intend to keep the fast for tomorrow in the month of Ramadan
2. After you break your fast
Allahumma inni laka sumtu wa bika aamantu wa alayka tawakkaltu wa ala rizq-ika-aftartu
O Allah! I fasted for You and I believe in You and I put my trust in You and I break my fast with Your sustenance