Question
One day in Ramadan, I woke up feeling acidity in my mouth that came from my stomach. Nevertheless, I do not know whether some of that acidity returned to my stomach or not because I was sleeping. Having woken up, I rinsed my mouth with a little water and the acidity disappeared. What should I do? Should I make up for that day?
Fatwa
All perfect praise be to Allah, the Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His Slave and Messenger.
Out of His Mercy, Allah does not hold His slaves responsible for what is beyond their capacity. He Almighty Says (what means): {Allah does not charge a soul except [with that within] its capacity.}[Quran 2: 186]
While sleeping, one's mind is absent and he cannot control his actions and therefore he is not responsible for anything - and this is the consensus of the scholars. The Prophet explicitly and clearly indicated this in the Hadeeth where he said: "The pen is lifted (i.e., stops recording deeds) from three (types of people): the sleeping person until he wakes up, the child until he reaches the age of puberty and the insane person until he becomes sane." [Abu Daawood and others - Authentic chain of narrators]
Consequently, you are not blameworthy for this and not required to make up for the day when something comes and returns to your stomach while you are sleeping. This is the Sharee‘ah ruling on such a case and is even more applicable when you are in doubt as to whether or not what you stated may have happened even did so.
May Allah reward you for your piety and keenness to do what is right.
And Allah Knows best.