To do what you will.
That's literally all it means, in an "urban" manner. To indulge in any manner of (usually rebellious or hedonistic) activity is to 'eat cake'. Thank Marie Antoinette, or some reasonable facsimile which has been lost to history, although she meant literal cake, the phrase has gained meaning since the dipshit didn't leave a record of what she actually meant.
Let them eat cake.
You're gonna eat cake (sarc).
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