I'm guessing by the question you're referring to the sachet found in Pokemon X & Y. The Pokemon you want to give this to is Spritzee who when given the sachet and traded will evolve into an Aromatisse.
Spritzee is a fairy type who can be found in both games in the Friend Safari. Aromatisse can only be found through the trade evolution so it's a worthwhile move if you plan on filling your Pokedex.
To get the sachet you need to head to the Skiddo Ranch on Route 12, don't forget to take a Pokemon who has learnt Cut. On the North-West side of the Ranch you will find a house that has a small set of stairs next to it. Between the house and the cliff there is a tree to cut down and then you will find the sachet and a whipped dream.
In X you will have two whipped dreams and one sachet. In Y you will find one whipped dream and two sachets.
