Do applying perfumes, deodorants, colognes or smelling this stuff break the fast? Or decrease its reward? Is it good not to do this while fasting? Furthermore, does using this stuff cause any problem for the prayers?
Applying/smelling perfumes, deodorants, colognes do not break the fast for it is not for the purpose of eating/drinking. But it should be avoided for that Allah commands: “These are the limits by Allah, so do not approach them. ” (Al-Baqarah/ The Cow 2:187)
There is no problem to offer prayers while the effects of those are on you.