Wait until ASU goes into Victory Formation the last few seconds of the game they'll shortly win.
At the final tick off the clock, and Yewties are throwing up surrender cobras, rip off your outer shirt to uncover your royal blue BYU shirt and shout: "Haha, you suck Utes! No Dominating the Big12 for you as you bragged you would!!"
Then calmly put your cover shirt back on and walk out of the stadium calmly, with the salty taste of Yewt tears all around you to savor.