When you break the fast say:

ذَهَبَ الظَّمَأُ وَ ابْتَلَّتِ العُرُوقُ وَ ثبَتَ الأَجْرُ إنْ شَاءَ اللهُ

Thahabath Thama-o wabtallatil ‘Urooq wa Thabatal Ajro Insha Allah

The thirst has gone, the veins have become moist, and the reward has

been established Allah willing.

This Hadeeth is Hassan and has been collected by Abu Dawood (2/306), Al Haakim (1/422), Al Baihaqee (4/239) and others.