Burger King have 2 single use (per account) coupons in their app. BOGOF Hershey's Chocolate Pie ending on 24th June. BOGO1/2P BK Chicken BLT ending 30th June. The prices in the title are from a store near me, yours could vary.
If you don't like bacon or tomato you could always remove it and get a regular BK Chicken although you'll only be saving about $1.85 for the 2 burgers then. (And they had a $5 BK Chicken deal a few days ago.) Be warned that the BK app is known to be problematic with some stores.
These aren't valid at Christchurch airport as always.
It's interesting that the BK Chicken BLT is a BOGO1/2 deal. They've generally had BOGOF deals in the app for their promotional burgers over the past 2 years or so. I wonder given the bankruptcy of the parent company if someone decided BOGOF for their promotional burgers was costing them too much compared to the likely benefit.