Although this is story related, I just thought I'd add a couple details. This requires both the gas can and the hose. While the gas can is easy to spot in Mo's garage, the hose is in the same place. However Ben has a habit of standing in front of it when entering Mo's garage. Just reposition him or move the cursor over it until it says "Hose".
As for the actual act to get the achievement...1. Touch the ladder on the tower to set off the alarm. Don't climb the ladder. Instead, hide behind the barrels in back left of the screen. After the vehicle lands, use the gas can. Then use the hose on the vehicle gas tank. Then use the mouth option on the hose.