Apple

When eaten in the Pokemon Mystery Dungeon games, they replinish up to 50 belly.

Locations in Explorers of Time, Darkness, & Sky
Apples can be found on all floors & at any shop in Waterfall Cave, Apple Woods, Craggy Coast, Mt. Horn, Serenity River, Amp Plains, Treeshroud Forest, Landslide Cave, Lush Prarie, Tiny Meadow, Sky Peak, Mystery Jungle, Marine Resort, Oblivion Forest, Southeastern Islands, & Inferno Cave. They can also be found on all floors of Chasm Cave, Dark Hill, Sealed Ruin, Dusk Forest, Brine Cave, Hidden Land, Temporal Tower, Crevice Cave, Star Cave, Labyrinth Cave, Surrounded Sea, Miracle Sea, Aegis Cave, Spacial Rift, Dark Crater, Mt. Avalanche, Sky Stairway, & Final Maze.
 * Mystifying Forest (all floors & shops on 1F-4F & even floors)
 * Lost Wilderness (shops on 1F & even floors)
 * Shimmer Hill (shops on odd floors)
 * Midnight Forest (shops on 1F-4F & even floors)
 * Mt. Mistral (all floors & shops on 1F & even floors)
 * Concealed Ruins (1F-28F)
 * Bottomless Sea (1F-48F)
 * Treacherous Waters (all floors & shops 16F-19F)
 * Zero Isle East (all floors except 20F & any shop)
 * Zero Isle West (all floors & all shops except 14F, 29F, & 40F)
 * Zero Isle South (all floors except 20F & any shop 1F-89F)
 * Destiny Tower (all floors except 20F & any shop)