Is the Sunnah to drink before eating?

There is nothing in the Prophet’s Sunnah to indicate that
it is mustahabb to drink water or sips of water before eating food.
Perhaps the one who thought that that is Sunnah imagined it because it is
proven in the Sunnah that it is mustahabb to drink in three draughts. But
this is something other than what the questioner thought, because the fact
that that is mustahabb has nothing to do with eating food. It is the same
whether one drinks before or after eating or whilst eating, or in any
other situation; it is mustahabb for him to consume his drink in three
draughts. 

It was narrated that Anas ibn Maalik (may Allah be pleased
with him) said: The Messenger of Allaah (blessings and peace of Allah be
upon him) used to breathe three times when drinking, and he would say: “It
is more thirst-quenching, healthier and more wholesome.” Narrated by Muslim
in his Saheeh (2028). 

Ibn al-Qayyim said: What is meant by breathing whilst
drinking is moving the vessel away from the mouth and breathing outside of
it, then going back to drinking. Zaad al-Ma’aad, 4/210. 

There are great wisdom and important benefits in drinking in
this manner. The Prophet (blessings and peace of Allah be upon him) drew
attention to them when he said: “It is more thirst-quenching, healthier and
more wholesome.” 

Thirst-quenching means it is more hydrating and beneficial. 

Healthier means it is better for one. 

Wholesome means that it is healing; it relieves one from
intense thirst and sickness to which that may lead, because it comes to the
stomach in stages one after another; the second draught soothes that which
could not be soothed by the first, and the third soothes that which could
not be soothed by the second. 

And it was said that wholesome means that it is free from any
disease or harm that may result from drinking in one draught. 

See: Sharh Saheeh Muslim by al-Nawawi, 13/199 

Ibn al-Qayyim said: One of the problems caused by drinking in
one draught is that there is a fear of choking, as the oesophagus may be
blocked by the large amount of liquid flowing through it. But if he breathes
slowly, then drinks, he will be safe from that. End quote. 

Zad al-Ma’aad, 4/231 

And Allah knows best.