Soma or the divine nectar is the secretion that is produced within the human body. In some traditions the kechari mudra is given a lot of importance for the nectar to be produced/released. I do not consider kechari mudra to be a necessity for the production of this nectar.

This nectar when produced, drips inside the mouth and is sweet. Initially it can be even salty. But it is mostly sweet and delicious. :) It is very well tangible. It gives the yogic practitioner a very beautiful state of mind and makes the body disease free. This nectar is even expected to transform the physical body into an immortal body if there is enough of secretion. But, the alchemy of transmutation of physical body is a slow process. Probably if one lives long enough, this could be achieved.

Read more here: https://jpalchemy.blogspot.com/2015/08/soma-or-divine-nectar.html