Well my coaches are against it on comp day. With adrenalin already running high naturally, it would send my heart racing like crazy (I had two red bulls at the last comp) and made it very hard to maintain control. You want calm and controlled aggression instead of your body getting into a crazy out of control fight-or-flight aggression. A clear mind is very useful when you're already nervous and not quite familiar with all this stuff as a novice to lifting competitions.
I don't know much about this stuff (some here know better) but isn't caffeine the exact opposite of anabolic, because of the increased cortisol level it induces?