This one is a bit odd, but Hungry Jacks offer a free BBQ Cheeseburger if you fill out the feedback survey at the bottom of their receipts.
You can ask people for their Hungry Jacks receipts since no one really bothered to do it, or even reads their receipt. Or you can find some in a bin if very desperate lol.
The survey only takes like 2 minutes and it presents you with a code for the cashier.

OMG I abuse this deal so much it is not funny!!!
Combine this with a $1 item (coffee if its morning, slushie if it's not or $1 onion rings if I am hungry) so you will always get a receipt.
AND- the shake and win hungry jacks app is awesome as well. If you know when to check in, you can score all the freebies (eg I know Wednesday mornings 7:45 or so will get me a free medium coffee at a specific hungry jacks)
Ozbargain has listed a whole site of birthday deals also - worth checking out.
https://www.ozbargain.com.au/wiki/list_of_birthday_deals7-11 app sometimes has free coffees and if you sign up you get a free krispy Kreme.
If you complete a 5 minute survey at Studentedge you can get a $10 giftpax voucher. Giftpax have a coffee pack (6x coffees at coles express for $9) which is awesome or you could do multiple for a better freebie (eg 3 wraps for $20 or so) - these are given as coupons with at least 4 months on them. While we are on the topic of student edge as well download their app and you can get a free medium soft drink/orange juice (or coffee in VIC) with any purchase over $3.
KFC and Maccas apps normally gives cheaper prices - sometimes they have free hot drink with any purchase or $5 off a $10 order etc
I'm sure there is more out there but this is all I've got off the top of my head
Yes, I have invested a lot of time into this
