The Piñata
Idea suggested by Sigillum Diaboli.
How do you transform a piñata into a truly attractive surprise for an adult? Easy, the magic word is "challenge." You need to turn the experience into a fun challenge. Sigillum's suggestion is to make each string of the piñata offer different alternatives for a written conversation. This way, only the correct answer will make the goodies inside the piñata fall out.
If you're good with crafts, you can make your own homemade piñata using a pretty paper bag (be careful to cover any logos it might have!). You can attach the fake strings with tape to the bottom of the bag so they come off easily. Make sure to secure the string with the correct answer well to prevent the surprise from slipping away.
As for the inside of the piñata, don't hesitate to delight the child in all of us with candies, but it wouldn't hurt to include some more adult and playful items to ensure the surprisee's happiness is complete :)