EASI (that Chinese food delivery service with the yellow logo - 悉尼送餐), will give you an $8 voucher to use with no minimum spend when you sign up via referral.
Cheap lunch/dinner sorted. Works for both pick up and delivery (though delivery fees may apply) and there is no minimum spend.
Lots of participating restaurants, they almost have a monopoly on the Chinese food delivery market.
Use the OzBargain referral links just below and punch in your (burner) phone number. Make sure you select the correct city because the coupon is region locked.
After that, you can login on the app via SMS code to use the voucher.
$8 coupon - Melbourne, Sydney, Adelaide, Perth, Hobart
$5 coupon - Brisbane, Geelong (sorry guys)
$300 worth of $5 delivery coupons - Canberra (sorry guys)
Also don't forget this bargain which is still running for more vouchers. There's no English banner but there's a screenshot of which banner to tap on.
EASI8 gets you $8 off your first order. That's the code they have up in all the venues.