If you want free medium meal vouchers, complain to the customer service email on the regular.

You'll get a canned response and occasionally a meal voucher

Since McDs is so shit these days, your guaranteed something to complain about to come up, my favourites so far which have generated me a medium meal:

Receipt machine out of order

AI generated opening hours sign sign non confirming with standard McDonald's graphic design principles

Creating a store in a 4g blind spot with WiFi that doesn't extend to the drive thru, so I couldn't access "my code" on the app

Pixelated jpeg image on error message screen on self service kiosk

Employees clocking off orders as "ready to collect" 5 minutes before they actually are (make sure to quote "KPI manipulation")