This achievement is tied to mission 7 - Secret Weapons. The list of vehicles to destroy are: Tank, Armored car, Truck, Motorcycle, staff car and gunboat.
There are many motorcycles patrolling the level but one is parked very near the standard start point, next to the shack up the hill. TNT or armored piercing rounds should do the trick.
The tank can be found next to the trenches slightly north of the standard starting point and one is outside the V2 wind tunnels where you kill Dr. Jungers. These require the use of either armored piercing rounds repeatedly to the rear of the tank or the use of a satchel charge to shred the rear armor and bullets to finish the job.
The staff car can be found patrolling the roads, however Dr. Jungers shows up at the V2 Wind Tunnel with a staff car. These are fairly simple to destroy with high explosives, though they can also be destroyed with Armored Piercing rounds to the front engine hatches.
Trucks are the most common vehicle driving on the roads throughout the level, though there is a gas truck parked outside the V2 guidance system across the street. A high explosive like TNT, a Panzerfaust or Teller mines will usually destroy a truck in one go.
The armored car is usually patrolling the roads throughout the level but I have found that it usually stops at some point and vehicles back up behind it making this one tricky. Armored piercing rounds to the engine hatches in the rear or a satchel charge will finish this one off.
As far as I know, there is only one gunboat in the level. It is patrolling the water near the V2 Capsule test site. On the rear of the boat are several explosive tanks that can be hit with rifle rounds (armored piercing recommended). Destroying 2 of them should make the boat explode, and if this is the last vehicle, net you your achievement and in-game medal.