Abu Hurayrah reported that the Messenger of Allah (peace and blessings be upon him) said:

Every action a son of Adam does shall be multiplied—a good action by ten times its value, up to 700 times. Allah says: With the exception of fasting, which belongs to Me, and I reward it accordingly. For, one abandons his desire and food for My sake.

There are two occasions of joy for a fasting person: one when he breaks his fast, and the other when he meets his Lord, and the (bad) breath (of a fasting person) is better in the sight of Allah than the fragrance of musk.

(Al-Bukhari)