From Bulbapedia, the community-driven Pokémon encyclopedia.
Poké (Japanese: ポケ Poké) is a type of currency used in Pokémon Mystery Dungeon world.
Poké is obtained by finding it on the ground in Mystery Dungeons or selling items to Kecleon Shops. Just like in the main series games, Poké can also be collected by using Pay Day.
Poké may be spent on various food items, TMs, and other goods in Kecleon Shops. Poké can also be spent at the Gulpin Link Shop, Wigglytuff Club, Croagunk's Swap Shop and Xatu Appraisal.
If the player or, prior to being able to change team leader, the partner, gets defeated inside a dungeon, the team will lose all of its current money. However, money kept at the Felicity Bank or Duskull Bank will not be lost.