This was done for a race, the route isn’t the best as it has some out and backs, but a great day out to see lots of Hong Kong.
Start at the peak, once you hit Wong Nai Chung Gap, turn left and do the big loop clockwise ending up back in Wong Nai Chung Gap. There is a petrol station with drinks and snacks there.
Recommended to stop here and refill on your way through. There are no other places to refill/get snacks so take what you need for the 2 halves of the route.
From Central Exchange Square bus terminus get bus no 15, or from under IFC get mini bus 1A (faster) get off at Peak Galleria.
When finished you can get the no 6 bus from Tai Tam Reservoir Road, Wong Nai Chung Gap Road Bus Stop, this takes you into Admirality then Central.