Q: If a person vomits and then brushes his or her teeth and used mouth wash while fasting and than thinks that the fast is broken, but doesn’t eat for the rest of the fast, is the fast valid?
A: If nothing was taken down the throat the fast will be valid.
If the person who has already commenced fasting merely intends to break his fast without physically doing so then the Fast will be valid and the intention void. (Shaami Vol.2 Pg.380)
And Allah Ta’ala Knows Best