Function GetPlayerVehicleID gets the ID of the vehicle the player is currently in.
NOT the model id of the vehicle. See GetVehicleModel for that.

int playerid The ID of the player in the vehicle that you want to get the ID of.

Return Values:
ID of the vehicle or 0 if not in a vehicle

//add 10x Nitro if the player is in a car. Might be called on a command.
new vehicle;
vehicle = GetPlayerVehicleID(playerid);
if(vehicle > 0)
    AddVehicleComponent(vehicle, 1010);

Related Functions
The following functions may be useful, as they are related to this function in one way or another.