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.
The scholars differed in opinion whether or not inhaling vapor invalidates the fast. However, even according to the opinion that vapor breaks the fast, your fasting is correct and you are not obliged to make it up for the following two reasons:
1- You are not sure that the vapor reached your throat or stomach, so in principle the fasting is valid and it is not invalidated just because of doubt; this is because the well-known Fiqh rule reads: “Certainty is not overruled by doubt.”
2- If we presume that some vapor reached your throat, you did so out of forgetfulness –as it appears from the question –and whoever eats or drinks out of forgetfulness, his fasting is not invalidated according to the correct opinion of the jurists . Therefore, your fasting is correct, Allaah willing.
For more benefit, please refer to Fatwa 85377.
Allaah Knows best.