Gate Your Thirst!
From Halopedia, the Halo wiki
Gate Your Thirst!
Gate Your Thirst! is an achievement in Halo: The Master Chief Collection. It is unlocked by finding and destroying the BLAST soda can on Stonetown on 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 "Stonetown" Multiplayer Emblem.
Location[edit]
On the bottom floor of the power station is some scaffolding with a blue tarp and two crates on top. The can is sitting between the two crates.