(hex:91) is a glitch item in Pokémon Red and Blue. It is a Rival's effect glitch item.
Its name is taken from what is normally the "Cancel" option in the inventory.
This glitch item has the same effect as a Lemonade in that it restores 80 HP to a Pokémon (both from outside of and within battle) but causes the Rival's effect outside of battle if the Pokémon menu is closed with B.