One can run the gamut from French to Zimbabwean cuisine in adjudicating which tradition offers the best apres dinner sweet treat in Sydney.
I have narrowed it down to two.
The best apres dinner treat in Sydney is arguably the "Cafe Gourmand" from
Baroque Bistro's menu which goes for only $10. For that price you get a coffee of your choice and your pick of any 3 flavoured macaroons. The macaroons are to die for. So good that I'm willing to stake my life that Baroque's macaroons (and thereby La Renaissance's) easily beat those of
Laduree, and it's in France... Baroque Bistro is successful offshoot of the successful and well-established
La Renaissance Patisserie in
The Rocks. Have your "Cafe Gourmand" indoors or out in the terrace, and treat yourself to a real sweet treat.

Baroque Bistro Macaroons, Image courtesy of Baroque Bistro website
The other of the best apres dinner sweet treat is the candied cassava dessert from
Home Thai restaurant in Sussex Street Sydney. Prepared marinating in cane sugar, it's served with this sugary "soup" and a coconut cream concoction. It's substantial enough to sate your hunger (if your dinner didn't quite get you there). Like the macaroons, you can team with a late night coffee/espresso, or stick with the team, and have some soothing herbal tea from your favourite part of the East.

Candied Cassava Treat from Home Thai Restaurant, Image Author's Own