It's super easy! You need a button with holes (not a shank), a bit of cord, e6000 cement, and the coin. Run the cord through the button. Cement the coin to the button, making sure that the cord will go the direction you need to run it through the bracelet (in this case, horizontally). Let the cement dry. It's best to hold everything together with a big chip clip. When it's dry, weave the cord through the cuff, centering the coin, then knot it on the inside of the cuff. Put a drop of cement on the knot, trim it when it's dry, and you're done.

The coins are relatively inexpensive unless they're older or Japanese. I can usually get them for a buck or two off ebay, or if you play the card game they often come packed with a thing of cards. There are tons of characters, colors, and finishes, and they come in two sizes (Raichu here is the small size). I've also seen people color them with enamel paint, which looks very cool.

This will work with any object that can cover a button, including money, flat back charms, keychain fobs, etc.