Does it cancel's my fast if I use an Inhaler as a means to pervent myself from getting sleepy?
Is it haram or is it allowable?
It is said in Islamic Fiqh Council, p. 213.
Inhalers are allowed in fasting and do not break it, as long as they are used in the respiratory route, not the digestive.
However, any medication (including inhalers) should not be used except in necessity.