Charlie Sheen's 'Tiger Blood' Revealed!

3/10/2011 5:15 AM PST

Xango -- Charlie Sheen's 'Tiger Blood' Revealed!

Charlie Sheen's kept his "Tiger Blood" cocktail a secret while waiting for an official sponsorship deal -- but TMZ has learned the secret beverage he's sipping is something called ... Mangosteen?!

Mangosteen is a rare Southeast Asian fruit -- and a puree of the stuff is bottled and sold as XANGO juice. The bottler claims the juice helps maintain intestinal, joint, and immune system health ... and also promotes a healthy respiratory system.

Charlie and health drinks may not sound like a perfect match, but friends close to Sheen tell us he "drinks the stuff everyday" -- and though publicly he's been referring to it as tiger blood ... privately he calls it his "mango drink."

As of now XANGO hasn't tapped Charlie to be a spokesperson. Sources connected with the company tell us they are "very nervous" about being associated with the actor.