What Are The Rage Candy Bars In Platinum For?

They are not obtainable legally, in the Platinum game.
On Pokemon Gold, Silver, and, I believe, Chrystal, you could buy them in mahogany town for $300. They healed your pokemon by 200hp.

Well what happened to me was that after i had done the legue and got heatran  3 legendary birds and dialga and palkia and giratina is that the professor was  standing next2 one of the stands on the left to the candy bar shop talk to him and he says something about them being out of stock talk to the person selling them and she will still say they are out of stock i think im not sure but i think that after about 200hour of playing the game you can buy them or they are available on a certain day like driffloon can only be got on Friday :) good luck

The rage thingy are rare in my game i bought one on sunday and it cost me 99999 to buy one trust me its wourth it it raise the stats by 10 each and the level by 5 but you got to complete the national pokedex then talk to rowan or oak one of them will say its common and give you a free sample