The places listed are only what I could find, and you should bare in mind that these are not necessarily all the places you can find Rare Candies. The Dowsing Machine appears to be of great use when it comes to obtaining items, so I recommend you use it frequently.
Johto
Route 34, Violet City, Ecruteak City with Dowsing Machine, Olivine City with Dowsing Machine, Mt Mortar with Dowsing Machine, Tin Tower, Whirl Islands with Dowsing Machine, Mt. Silver with Dowsing Machine, Shining Lighthouse.
Kanto
Route 27 and 28 with Dowsing Machine, Vermilion City Fan Club President, Cinnabar Island Dowsing Machine, Indigo Plateau with Dowsing Machine, Cerulean Cave with Dowsing Machine, Victory Road.
Shops
Johto: Battle Frontier, Pokéathlon Dome.
Total of 16, not including the shops.
well you are going to have to have the rare candy cheat because you can get heaps or get them from the pokealathon
at the pokeathalon
you can find rare candies anywere in kanto and johto. You just have to be lucky
You find them hidden in the game.
look behind you
4426543653345634
in the pokeatolon on Mondays and Saturdays.
Use your dowsing machine and look hard!
no you can't without an AR.
No such thing Yet
Rare Candies Are Used To Level Up A Single Pokemon By 1Lvl.It said wher are rare candies not what!
buy an action replay
Either save them up or use an a r code.