50 Cent: I Flossed on Instagram with Fake Cash

50 Cent may not the P.I.M.P. he pretends to be ... because when he shows off his cash on Instagram, it's as fake as Courtney Stodden's boobs.

The rap star has responded in court docs filed Tuesday to allegations he's hiding money from his creditors in his bankruptcy case. The creditors saw 50's slew of social media posts in which he showcased stacks of money.

But 50 now says the Benjamins are phony pics and he's not hiding assets ... it's all for show, to maintain his persona. However, last week he filed documents showing the court he has 65 MILLION in assets.