High Altitude Thirst!
From Halopedia, the Halo wiki
High Altitude Thirst! is an achievement in Halo: The Master Chief Collection. It is unlocked by finding and destroying the BLAST soda can on Zenith Halo 2: Anniversary multiplayer. The achievement is worth 5 Gamerscore and can be unlocked in both matchmaking and custom games, though the latter is much more advisable. It also unlocks the "Zenith" Multiplayer Emblem.
The can is sitting on a ledge beneath the Sniper Roost/Little Tower, below plane of the map.