I'm in the UK and have McDonalds semi-regularly. A few times a month at least. Get a receipt, fill out the online feedback form, get a code. Put the code in the app, get an offer for £2.99 sandwhich (McPlant, Big Mac, whatever the chicken thing is) and either fries or a salad. £2.99 for a McPlant and fries at 3am is a godsend.