As a proud sponsor and Austin-based brand, C4 Energy is excited to bring unlimited energy to SXSW and fuel eventgoers throughout their action-packed weeks with the perfect pair from our beverage lineup– C4 Smart and C4 Ultimate Energy. C4 Smart Energy is your daytime boost to Stay Focused throughout panels, networking, and everything in between. As the only energy drink with clinically proven mental benefits, it’s the perfect drink for the SXSW crowd. Nights come alive with C4 Ultimate Energy, the Supercharged Energy drink with 300mg of caffeine, ensuring unforgettable concerts, parties, and after-events.