Offer valid only on 6/4/2026 at participating U.S. Smashburger® locations. Offer available for purchases made in-store or online through smashburger.com or Smashburger® app during regular business hours. Store hours may vary. Offer to receive one (1) complimentary loaded upgrade (cheese sauce, bacon cheese, chili cheese, chili cheese jalapeno) to any regular size side order (not including applicable taxes).  For in-store orders, must mention offer at checkout to redeem offer. To redeem offer online, must enter promo code FREECHEESE at checkout. Offer does not apply to any applicable sales tax or large sized side orders. Not valid on catering orders or orders with third party delivery. Cannot be used in conjunction with any other offer, promotion, or discount. Not valid on previous purchases. No cash value (unless prohibited by law, then cash value is $.005). No substitutions. No rainchecks. Company reserves the right to withdraw or change the offer’s terms and conditions at any time, at Smashburger’s discretion, and without notice. While supplies last. © 2026 Smashburger IP Holder LLC. All rights reserved.