From Anas: “The Prophet (ﷺ) prohibited that a man should drink while standing.” (Qatadah said:) So it was said: “And eating ?” He (Anas) said: “That is worse.”
[Abu ‘Eisa said:] This Hadith is Hasan Sahih.
: Sahih (Darussalam)
: Jami` at-Tirmidhi 1879
: Book 26, Hadith 19
: Vol. 3, Book 24, Hadith 1879
On this one here’s a link to check out the scientific benefits of drinking water while sitting..
(Note: Your love for the beloved messenger(Saw) should be enough to follow the Sunnah, but sometimes you need to know).