From the Super Mario Wiki
“Have you tried our world-famous Pi'i-latte yet? It's made from certified organic Pi'illo Island beans. Jam-packed with the nutrients your body needs. One sip and you'll be a true believer. It's much better value than buying healing items.”
Shopkeeper, Mario & Luigi: Dream Team

Pi'i-lattes are coffee-like drinks in Mario & Luigi: Dream Team that don't physically appear during the events of the game and cannot be stored as an item. A Pi'i-latte fully restores the HP and BP of both Mario and Luigi and can be found in the shops in the Real World on Pi'illo Island as well as shops in the Dream World for players to buy for 10 coins.

Buying a Pi'i-latte is equivalent to Mario and Luigi both using a Max Candy on themselves, taking a nap in the Pi'illo Castle or Wakeport inns, or Mario and Luigi drinking from the fountain in Mount Pajamaja or Dreamy Mount Pajamaja. Additionally, the shops in Pi'illo Castle, Dreamy Pi'illo Castle, Wakeport and both the Gold and Silver Shops in Driftwood Shore are the only shops on the island that don't have Pi'i-lattes, but in Pi'illo Castle and Wakeport, the aforementioned inns are its replacement, and in the Gold Shop's case, Rose Hip Tea is used as its free replacement.