Here is the answer I had in mind:
BEERUS - a fictional character in the Dragon Ball universe, Beerus is the God of Destruction of Universe 7.
It's not possible to drink my first three:
How do you drink a bee?
But possible to drink my first four:
Indeed; however, moderation should be exercised :)
My last four are meaningless, it seems:
erus ... ???
Unless their meaning is sure:
Flip it around, you get sure.
I have the perfect number of letters:
6 is a perfect number.
My powers can destroy once and for all:
Beerus usually uses his power to destroy planets, but he is strong enough to destroy entire solar systems with ease (as said by Whis when describing Beerus' might when angered).
Am I real? In a way, you see:
Beerus is a fictional character, so he's "real" in a way.
Just don't place your hopes on a ball:
The series revolves around the collection of "dragon balls". They are orange, crystalline spheres with the ability to call forth the Eternal Dragon who can grant wishes to anyone who gathers all seven of them. (placing your hopes on a ball)