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If held by a Pokemon, will automatically cure the sleep status condition when inflicted on the holder. Consumed after use. Can also be used forcibly by the trainer in-game. Natural Gift becomes a 60 Base Power Water-type attack when the user holds this Berry, but the Berry is consumed after use.
A Chesto Berry is a pretty good item. While it is not recommended to carry this purely for the sake of sleep, as in that case Lum Berry is a better choice for its ability to heal any status, not just sleep, it does have one significant advantage for one particular strategy: ChestoRest. This strategy revolves around a bulky Pokemon boosting until it is nearly dead, and then using Rest to recover from all damage and status, and then immediately healing itself with Chesto Berry. This strategy would not work if Lum Berry were used, as then the Berry could be removed if the Pokemon were inadvertently poisoned. Notable users of this strategy include Volcarona and Kingdra.
Nacrene City - 3 Chesto Berries received from Cheren.
Studio Castelia in Castelia City - show Harlequin a Pokemon of the type he asks for.
Dream World (Sparkling Sea).