"Do what you want!"
Translation:Faites ce que vous voulez !
The "tu" imperative is fais; "faites" is the vous imperative. The word faisez does not exist.
It's so annoying getting marked off for sentences that are correct. Fais comme tu veux (how is this wrong I have heard it so many times in French)
ce que is a relative pronoun like que, but here it serves as an indefinite direct object.
It is used in sentences in which there is no expressed antecedent. It does not refer to a specific noun, but rather to an idea or an entire statement, which may or may not have been previously expressed: it refers to something unstated and unspecified.
Compare it to a sentence with an antecedent:
Faites du sport que vous voulez ! → "Do the sport that you want!"
Just to add to your explanation:
usually when the word what comes in the middle of a sentence you use ce que. However, when ce que means what it only ever comes before a pronoun, so if what doesn’t come before a pronoun then you use quoi or ce qui
Je ne sais pas ce que je peux demander. - I don’t know what I can ask
Je ne sais pas quoi demander. - I don’t know what to ask
je ne sais pas quoi faire - I don’t know what to do
fais ce que tu peux - do what you can
Envoie-leur ce qui était prévu. - Send them what was planned.