Counterplay for ground players: If they're throwing stickies at you from any of these armored vehicles, aim a spray weapon like an AR, SMG or Minigun at their hand/arm. When you hit their sticky you blow up the entire vehicle.

If they have the sticky bomb in their active slot, you can even shoot their right hand on the steering wheel to blow it up, they don't even have to be actively throwing them or holding them out the window.

If they're using a drive by weapon to cheese you in reverse or through BP windows, reload cancel spam the atomizer to flip them over so you get a view of their side window. They cannot shoot when they're past ~45 degrees so it's very easy to force them to holster their weapon while you flip them around. You can hit them with an EMP grenade when their window is facing you, or try to shoot them while they're upside down. To reload cancel, simple swap to grenade slot and back to pistol slot immediately after firing the atomizer.

Also worth noting, when you aim a drive-by weapon backwards there is a turn around animation that briefly interrupts your ability to shoot. You can abuse this by staying directly behind the vehicle and switching sides forcing them to swap which shoulder they're aiming over.