stock FindClosestVehicle(playerid)
{
    new
        Float:x, Float:y, Float:z,
        closest = -1;

    for(new a = 0; a < MAX_VEHICLES; a++)
    {
        GetVehiclePos(a, x, y, z);

        if(a != YOUR_VEHICLEID_OR_ARRAY/VARIBLE && IsPlayerInRangeOfPoint(playerid, 10.0, x, y, z))
        {
            closest = a;
        }
    }
    if(closest != -1) return closest;
    
    return INVALID_VEHICLE_ID;
}