Free Sonic Cheeseburger with purchase of Sonic Cheeseburger at regular price Redemption Instructions Log in to view the redemption instructions for this offer. Participating locations include: SONIC 2299 N Imperial Ave El Centro, CA 92243 Phone: 760-353-0042 Map SONIC 2299 N Imperial Ave El Centro, CA 92243 Phone: 760-353-0042 Map Sharing Options Share Offer Copy Link