Similar to this https://www.ozbargain.com.au/node/426714 but in AUD and you can use both on same account and card.
Redemption Period: 12:01am AEDT December 22, 2018 to 11:59 pm AEDT December 26, 2018, limited quantity, strictly while supplies last.
Travel Period: The travel dates must be between December 22, 2018 and December 31, 2018 (inclusive).
Buy any activity/thing to do (tickets to zoo, tours etc) for $30 or more and get $25 off (can be 1 or more tickets)
One per account/email and one per Credit/Debit card number (accounts are easy to create so your limited to the number of cards you have)
Booking must start and finish before 31/12/18 (if you book free cancelation tickets you can email/call the provider and change the dates to some time in 2019 (this has work for me 4/5 times in the past and the 1 it didn't Expedia allowed me to change the date with them)
Enjoy while it lasts !
Some good ones in Sydney:
Taronga Zoo + 2 Day Hop on Hop off ferry $30.46
Sydney Aquarium ~$19
Luna Park 3 Rides, 3 Games + $10 for Food/shopping ~$27
P.S Don't book the Sydney Tower Skywalk as its closed (and has been for like 6 months)