Is it obligatory to make up for a fast (qaḍāʾ) for someone who doubted whether something entered his throat while fasting, whether it was oil or lip balm, or who accidentally inhaled deodorant spray while fasting?

Your fast is valid, and you are not required to make up for it, as long as you did not ascertain that something invalidated your fast, and you did not intentionally inhale the spray. Fasting is not invalidated by doubt or by accidentally committing an act that breaks the fast. The conditions for invalidating a fast with a fast-breaker are: knowledge, remembrance (not forgetting), and intention.