Would $2500 USD be enough for 1 week in Sydney?

Yes. Assuming you already have the round trip plane ticket. $2500 USD After you arrive is just fine.

You will need accommodation. You can get budget accommodation for $100 a night or less so allow $700 for that. There are plenty of places to get good food at reasonable prices in Sydney so allow $15 for breakfast, $25 for lunch and $40 for dinner and that's $560 for the week. To find good food at the budget end, Google "Cheap eats in Sydney". If you eat cheaply some nights, you can splurge on a top restaurant on others. Get a copy of the Good Food Guide in any newsagent to find highly rated restaurants.

You will probably want to take at least a day trip to the Blue Mountains. Prices for those vary but you'll get a good trip for $100 - $150. Climbing the Sydney Harbour Bridge varies from $268 to $388 depending on the time of day. Check what's on in Sydney https://whatson.cityofsydney.nsw.gov.au/ for events, shows etc that will be happening while you are in the city and check prices too. A big show or something on at the Opera House will set you back about $250 but there are cheaper shows around. A visit to Taronga Zoo, which is a must, will cost you about $50 including the cable car to the top.

When you arrive in Sydney, get yourself an Opal Card and put at least $50 on it. You will use it for buses, trains, ferries, light rail and metro to get yourself round Sydney. You can top it up as needed. Don't hire a car in Sydney, public transport is very good and there are always taxis or Uber.

You can see Sydney very well for $2500 for a week provided you are not spending $300 a night for a hotel. Go for budget accommodation and you will be fine.

By the way, tipping in Sydney is not required. You can tip if you want to but if you don't, no-one will mind, even taxis. You certainly don't tip bar staff in pubs or bars. We pay our workers a living wage so tipping is not necessary.

Thats plenty and if you can't survive on that then you must be loose with your coin

i dont see why not

Australian restaurants seem to think they serve the nectar of the gods these days, so be careful where you go for a bite.

nope, but it would be enough for 1 week in montreal