A peculiar apple that can make a certain species of Pokémon evolve. It's exceptionally sweet.
Acquisition
Tapping apples that appear near PokéStops can award either Sweet Apples, Tart Apples, or an encounter with a wild Applin. Apples will also have an increased chance of appearing at PokéStops with Mossy Lure Modules.
Merchandise
Pokémon School drawstring bag (upper-left corner)
A Sweet Apple is seen in the artwork for the Pokémon School merchandise collection exclusive to the Pokémon Center.