Placing a betel-leaf in the mouth

Question:

A fasting person placed a tobacco-containing betel-leaf in his mouth
but is not swallowing its liquid. Does his fast break?

Answer:

If he perceives the taste of the betel-leaf in his throat and he swallows
it, the fast will break. But if it reaches his throat and he does not
swallow it, the fast does not break. No matter what, it is certainly
makruh tahrimi. Generally it goes down the throat.

Jawahir al-Fatawa:

The effects of a huqqah, betel-leaf, snuff and other similar things
which are placed in the mouth for a specific purpose generally go
down the throat. The fast will therefore be invalidated. If a person
takes extreme care to ensure its effects do not go down the throat, it
will still be makruh tahrimi due to the doubtful nature of this action.1

Imdad al-Ahkam:

Placing powdered tobacco in the mouth while fasting:

We learn from this that to use powdered tobacco for the teeth in such
a manner that it definitely does not go down the throat will not
invalidate the fast. And if the slightest amount goes down the throat,
the fast will be invalidated. Anyway, it is makruh to use powdered
tobacco while fasting if there is no need to use it. If there is a real need
to use it, it can be done after maghrib.2

Allah ta‛ala knows best.

REFERENCE:

1 Jawahir al-Fatawa, vol. 1, p. 28.
2 Imdad al-Ahkam, vol. 2, p. 128.