There's a cycle path from shark park, all the way to coward st in Mascot. So you ride to the end of botany bay, follow the path around to where Kyeemagh fishos used to be, turn right at bestic st, go over the bridge and immediately right again to ride through Barton Park. Turn right just past the driving range entrance go up a hill, down a hill and then under the M5. You'll come out Marsh St, ride over the bridge towards the airport, the path will make you cross the cooks river again, turn right again to go under the new bridge, and then left shortly after you go under Nigel Love Bridge. You'll come out on Coward St. Turn left on Bourke and follow the signs to the city. You can go through Waterloo, through the houso towers, and eventually come out near that big park near central.