The Stamina Vessel is an item in The Legend of Zelda: Breath of the Wild. It can be obtained by returning four Spirit Orbs to Hylia's Goddess Statues. Through the statues, Hylia will offer to trade Link either a Heart Container or Stamina Vessel in exchange for four Spirit Orbs. Goddess Statues can be found in villages, the Temple of Time, and Forgotten Temple.
However later on Link encounters the Horned Statue in Hateno Village in "The Statue's Bargain" which is a Demon who was sealed inside a statue by Hylia long ago for making life-for-money bargains. The Horned Statue steals one of Link's "Essences" (a collective term the Horned Statue uses to refer to both Heart Containers and Stamina Vessels), however Link finds the Statue only wishes to do business with Link and will take one of Link's Essences and gives him the option of purchasing either a Heart Container or Stamina Vessel, essentially allowing Link to change his mind after he has already investing his Spirit Orbs, allowing him to swap Heart Containers for Stamina Vessels and vice versa in exchange for payment in Rupees. Link can complete the side quest by purchasing back the "Essence" the Statue took or trade it for a different one. After the side quest is completed Link can return to the Horned Statue near Firly Pond (located northwest of Link's House) at any time to trade "Essences".