If Biden is obviously hopped up on something Trump should note that. He could say "Before I answer that question, let me say that Biden's obviously high as a kite just like in his State of the Union address".
Could work ... any words or phrases with the potential to “set him off” Trump should carry in his back pocket ... to be delivered “sweetly”, of course. It will be interesting — and not a little entertaining — to watch the “independent” moderators attempt to deploy their bail-biden-out directive to save F-Joe Biden from himself. (I still don’t truly understand what purpose this “debate” serves the Democrat/Communist Party cult leaders .... lots of conjecture, though.)