What should I see in Sydney if I only have two days?

Let the forecast decide your second day. A ferry to Manly adds a harbour journey to a beach visit, while Bondi makes sense if a coastal walk is the priority. If the weather turns, shorten the exposed walk and spend more time over a meal or at an indoor attraction. Two good, unhurried areas will be more memorable than trying to tick off every suburb in one afternoon.

Keep the first day within walking distance of the harbour instead of crossing town for every landmark. Circular Quay, the Opera House, the gardens and The Rocks fit together naturally, with plenty of places to pause for lunch. I would make just one timed booking, if any, and leave the rest of the day open. That gives you a better chance of enjoying both the view and a relaxed dinner.

Give the first day to the harbour. Start at Circular Quay, walk around the Opera House and Royal Botanic Garden, then cross to The Rocks. If you still have energy, walk the Harbour Bridge pedestrian path for a second perspective; the paid BridgeClimb is a separate choice, not a requirement. Circular Quay and The Rocks give you plenty of places to stop for lunch or dinner without losing time in transit.

On day two, choose one longer outing: take the public ferry to Manly for a beachside meal, or head east for Bondi and a coastal walk. Both are good days, but trying to cover both along with the harbour icons can turn the visit into a timetable. Leave room for the weather and for a neighbourhood you discover along the way.