From Pikipedia, the Pikmin wiki
The Succulent Mattress (スイート・クッション?, lit.: "Sweet Cushion") is a treasure in Pikmin 2. It is actually a large marble cookie. It is found in the third floor of the Submerged Castle, near many electrical hazards, making Bulbmin useful to retrieve it.
“A while back, I didn't sleep for days. My stomach was roiling and my head was cloudy. I couldn't rally any motivation! The only thing I could muster is a sigh. Then I found this mattress! When I reclined on it, I fell asleep immediately and had the sweetest dreams.”
“Sweet to the taste and touch! Sleep on this magical mattress and dream of a land of sweets.”
Names in other languages