Praise be to Allah.
Can you use siwak and toothpaste while fasting?
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
“As for the miswak, it is permissible and there is no difference of opinion concerning that. But they differed as to whether it is makruh after the sun has passed the meridian, and there are two well known views, both of which were narrated from Ahmad. But there is no shar’i evidence suggesting this to be makruh which can be regarded as an exception from the general meaning of the texts about the miswak.” (Al-Fatawa al-Kubra (2/474)
Can you use perfume while fasting?
The scholars of the Standing Committee for Issuing Fatwas were asked:
Can the fasting person wear perfume? Is it permissible for him to use the miswak during the day? Can a woman put henna or oil on her hair?
“He may put perfume on his clothes or on that which he wears on his head or body. But he should not put it in his nose.
He may use the miswak during the day, because the Prophet (peace and blessings of Allah be upon him) said: “Were it not that it would be too difficult for my ummah, I would have told them to use the miswak before every prayer.” Sahih – agreed upon. This includes Zuhr and ‘Asr prayer for the one who is fasting and for others, and we do not know of any sahih evidence to suggest that this is not allowed.
A woman may put on henna or put oil on her hair, because that does not affect the fast. A man may also apply medicine and so on, even if he is fasting.” (Fatawa al-Lajnah al-Daimah, 10/328)
Shaykh Ibn Baz (may Allah have mercy on him) was asked: What is the ruling on using toothpaste when fasting?
“Cleaning the teeth with toothpaste does not break the fast as is the case with the miswak. But one should be careful to avoid letting any of it reach his throat, but if that happens accidentally then he does not have to make up the fast.” (Majmu’ Fatawa al-Shaykh Ibn Baz (15/260)
And Allah knows best.