Gate Your Thirst!
From Halopedia, the Halo wiki
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.
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.