Rule Your Thirst!
From Halopedia, the Halo wiki
Rule Your Thirst!
Rule Your Thirst! is an achievement in Halo: The Master Chief Collection. It is unlocked by finding and destroying the BLAST soda can on Warlord in 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 "Warlord" Multiplayer Emblem.
Location
On the top level at the yellow side of the map, there is a tree root which is growing down into the back right corner (when viewed from the center of the map). The can is sitting in a crack in the wall just behind the tree root.