I get cramps in the chest, this causes the need to drink water. What is the ruling if this happens while I am fasting? Please note that this happens to me even while I am not fasting because of smoking.

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, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

If the lump in the throat is too severe to bear and you have to relieve it, then it is permissible for you to relieve it. Rather, you are required to relieve such a lump in the throat if you fear that it may cause you to die. This is one of the excuses for which fast-breaking is allowed. Yet, you have to make up for the days that you come to miss. If the lump  in the throat is bearable, then you are not allowed to break your fast. If you do so, then you have to make up for that fast and turn to Allaah in repentance.

Finally, we would like to evoke your attention to the fact that smoking is prohibited because it brings about harmful consequences. 

Allaah Knows best.