Hi.. Thanks for the query.. Many individuals have a sensitive soft palate and when you brush your teeth, the brush can touch the back of your mouth and also there is accumulation of saliva and water while gargling.. It can cause a reflex sensation and there can be vomiting.. The watery fluid can be acid that must be coming up due to gag reflex.. You can minimise the effect by brushing your teeth first and try not to go too far back. You can clean your tongue using a tongue scraper and to avoid gagging protrude your tongue out of mouth and use short intermittent strokes in cleaning the tongue.. Breathe through nose deeply while gargling.. Move the fingers of your feet and clench your fingers of hand to divert attention.. Hope this helps.. Regards.