When used from the satchel on a Pokémon, it restores the PP of one of its moves by 10. When thrown from the satchel for a wild Pokémon to eat, its reactions will be dulled, causing them to be less aware and not notice the player as easily.
The following items can be crafted using the Hopo Berry:
The Hopo Berry's design and name may be based on hop.
The Berry's ability to dull a Pokémon's reactions and cause them to not notice the player may be a reference to alcohol intoxication, as hops are used in brewing beer. Intoxication can dull one's senses, including impaired eyesight, smell, and hearing.