Fast lv up

What is the fastest way to level up from level 85 to 100 ?

Without just cheating in Rare Candies, I'd say the best way is to give it a Lucky Egg to gain extra experience after battles.

Rematch the gym leaders, rematch with the E4, rematch with Red (for G/S/C/ & HG/SS) or have them hold a lucky egg while doing the ones I mentionned.

Without knowing what game this is for, I can't accurately tell you what to do or where to train. I'll lock this for now, since you have decent answers, but if you need more specific information, try asking in the correct Q&A thread. For example, if this is for Black 2, ask in the Black and White 2 forum's Q&A thread. :)

Locked.