This works in both single player and multi-player....

What you do is this, take out your battery powered drill if you have one on you (the drill is normally used to fix vehicles) but the drill can also destroy them.
The only time you can destroy a vehicle is when an enemy is inside it, for instance sneak up to an enemy vehicle start drilling or jump onto it and start drilling, the vehicles health will rapidly decrease and then explode.

While trying this in single player be careful and make sure that the enemy cannot shoot you while you are on the vehicle because if you stand next to an enemy vehicle it will try shoot at you (the heavy and medium tanks will try shoot you only with the machine gun on top).
Sometimes they will start to drive away to get a better shot at you so you should just stick to jumping on the vehicle and drilling it.

But in multi-player the enemy will just jump out of the vehicle and try kill you or just back up and ride over you.

The drill can also destroy walls, fences, poles (wood and metal ones), trees, concrete barriers, so no need for a grenade launcher!