If you based in Sydney and close to the city, you might already order from UberEats. it is an App from famous ride-share company Uber.
Basically, the App allows you to order from various signed restaurants closer to you and they deliver the food using uber riders.
Use Our Coupon Code to get $20 off from your order = eats-donh3517ue
Currently, they introduced Promo code to get Free $20 worth of food by referring people to the App. normally both referrer and receiver both get $20 on their UberEat account and they can use $20 to order food.
Uber used this method to their Uber Taxi and it really worked. most silicon valley companies like DropBox use this method to gain faster user registrations. UberEarts spending average $40 to gain new register using this method.