test.yml

InstanceId:
  Condition: DoLaunchInstance
  Description: Stack Instance ID
  Value: !<!Ref> Box
  LaunchConfig: !ImportValue "my-import-value"
  UserData: !If
    - DoWriteConnectionString
    - !Base64
        Fn::Sub:
        - |
          #!/bin/bash -xe
          cfn-init -v --stack ${AWS::StackName} --resource Box --region ${AWS::Region}
          cfn-signal -e 0 --stack ${AWS::StackName} --resource Box --region ${AWS::Region}

Outputs:
  Output1:
    Description: "Some quoted string"
    Value: !Sub
      - Instance ID is ${SomeVar}
      - {SomeVar: !Ref InstanceId}

  Output2:
    Description: Some unquoted string
    Value: !Sub Instance ID is ${InstanceId}

  Output3:
    Description:
      Fn::ImportValue:
        "Fn::Join": ["", [My-, !FindInMap [Very, !Ref Long, String]]]
    Value: !ImportValue
      "Fn::Join": ["", [My-, !FindInMap [Very, !Ref Long, String]]]