//Device class
class Device extends Model {

    /**
     * The attributes that are mass assignable.
     *
     * @var array<string>
     */
    protected $fillable = [
        'type',
        'device_data'
    ];

    public function device_data()
    {
        return $this->embedsOne(DeviceData::class);
    }
}

// DeviceData class
class DeviceData extends Model {
    /**
     * The attributes that are mass assignable.
     *
     * @var array<string>
     */
    protected $fillable = [
        'field1',
        'field2'
    ];
} 

// code
$device = Device::find('66926851514af3dfe500d659');
$data = $device->device_data;
$data->unset('field1');
$data->update();

// However, the generated query is incorrect:
db.devices.updateOne({"_id": ObjectId("66926851514af3dfe500d659")}, {"$set": {"device_data.$unset": {"field1": true}}})

db.devices.updateOne({"_id": ObjectId("66926851514af3dfe500d659")}, {"$unset": {"device_data.deviceType": true}});