All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Crying does not invalidate fasting, however, if crying is due to discontentment with the Decree of Allaah, like crying when a calamity befalls a person, and crying which is accompanied by slapping one's cheeks or tearing one's clothes, then this may decrease the reward of fasting.
For more benefit on the things which invalidate fasting, please refer to Fatwa 85377.
Allaah Knows best.