Manipulating a Column Containing Key/Value Pairs

UPDATE

If as you posted in your own answer you're able to use a UDF to get specific key values let me suggest this one: (You don't need to split all key/values and you don't need to read the table again, you can get it by using text functions.)

CREATE FUNCTION fnGetKey(@Data text, @Key varchar(20))
RETURNS varchar(100)
AS
BEGIN

  RETURN
  (
  SELECT 
      SUBSTRING (
                  @Data,
                  /* Position of first '=' after key + 1 */
                  CHARINDEX('=', @Data, PATINDEX('%' + @key + '%', @Data)) + 1,
                  /* Lenght, Position of first chr(13) after key less previuos value - 1 */
                  (CHARINDEX(CHAR(13), @Data, PATINDEX('%' + @key + '%', @Data)) 
                  - 
                  CHARINDEX('=', @Data, PATINDEX('%' + @key + '%', @Data))) - 1
                )
  )

END

SELECT
    FruitID, Name, Description,
    dbo.fnGetKey([Data], 'key 2') as [key 2],
    dbo.fnGetKey([Data], 'key 4') as [key 4]
FROM
    [Fruit];

FruitID | Name   | Description | key 2   | key 4  
------: | :----- | :---------- | :------ | :------
      1 | Banana | Delicious   | value 2 | value 4
      2 | Pear   | Rotton      | value 2 | value 4
      3 | Kiwi   | Okay        | value 2 | value 4

db<>fiddle here

Original answer

The only solution I can figure out is by splitting key/values and then pivot it to obtain the desired result.

Unfortunately there are some inconveniences:

• STRING_SPLIT doesn't works with text columns. Hence you must cast it to varchar before you are able to manipulate it.
• STRING_SPLIT requires a nchar(1) or nvarchar(1), ergo you should replace CHAR(3)+CHAR(10) by a single character.
• Aggregate function on PIVOT works better with numeric values, then you should cast Value to some numeric data type.
• PIVOT needs a well-known number of columns, in my example I have used a few of them but you should write the whole sequence unless you'd rather deal with dynamic queries.

This is what I've got using your sample data:

WITH KP AS
(
    SELECT FruitID, Name, Description, value as KPair
    FROM   Fruit
    CROSS APPLY STRING_SPLIT(REPLACE(CAST(Data AS varchar(max)), CHAR(13)+CHAR(10), ','), ',') /* STRING_SPLIT only allows nchar(1),  varchar(1) */
)
, KP1 AS
(
  SELECT
      FruitID,  
      SUBSTRING(KPair, 5, CHARINDEX('=', KPair) - 5) AS [Key],
      SUBSTRING(KPair, CHARINDEX('=', KPair) + 7, LEN(KPair) - CHARINDEX('=', KPair) - 6) AS [Value]
  FROM
      KP
)
SELECT [FruitID], [1],[2],[3],[4],[5]
FROM   KP1
PIVOT (MAX([Value]) FOR [Key] IN ([1],[2],[3],[4],[5])) AS PVT;

First CTE split every Key X=Value Y. The second one cut this value to obtain each [Key] and [Value]. And the final PIVOT compose the final result in columns.

FruitID | 1  | 2  | 3  | 4  | 5 
------: | :- | :- | :- | :- | :-
      1 | 1  | 2  | 3  | 4  | 5 
      2 | 1  | 2  | 3  | 4  | 5 
      3 | 1  | 2  | 3  | 4  | 5 

db<>fiddle here

NOTE: I'm not sure if I should maintain [Key 1] & [Value 1] or it should be converted as a column named [Key] & [Value].

A different approach

When I work with 3rd party databases I usually add a new database, on the same server/instance if possible, and then I use it for my own purposes, just to avoid conflicts with the DB owners.

In this case you could add a new table and periodically throw a process to update it with the new values.

You could use a table with all columns:

CREATE TABLE [FruitKeys]
(
    [FruitID] int NOT NULL PRIMARY KEY,
    [V1]      int NULL,
    [V2]      int NULL,
    [V3]      int NULL,
    [V4]      int NULL,
    [V5]      int NULL
);

or a table with Key/Value pairs and use a pivot to obtain the final result:

CREATE TABLE [FruitKeys]
(
    [FruitID] int NOT NULL,
    [Key]     int NOT NULL,
    [Value]   int NOT NULL,
    CONSTRAINT [PK_FruitKeys] PRIMARY KEY ([FruitID], [Key])
);

It seems to me that the source data is not that far from JSON format.

You could convert it pretty directly then use OPENJSON to produce a relational output:

SELECT
    F.FruitID,
    F.[Name],
    OJ.[key 1],
    OJ.[key 2],
    OJ.[key 3],
    OJ.[key 4],
    OJ.[key 5],
    F.[Description]
FROM dbo.Fruit AS F
CROSS APPLY OPENJSON
(
    -- Convert source data to JSON format
    '{' + 
        CHAR(34) + 
        REPLACE
        (
            REPLACE
            (
                CONVERT(varchar(max), F.Data), 
                '=', CHAR(34) + ':' + CHAR(34)
            ), 
            CHAR(13) + CHAR(10), 
            CHAR(34) + ',' + CHAR(34)
        ) + 
        CHAR(34) + 
    '}'
) 
WITH
(
    [key 1] varchar(100),
    [key 2] varchar(100),
    [key 3] varchar(100),
    [key 4] varchar(100),
    [key 5] varchar(100)
) AS OJ;

Output:

FruitID | Name   | key 1   | key 2   | key 3   | key 4   | key 5   | Description
------: | :----- | :------ | :------ | :------ | :------ | :------ | :----------
      1 | Banana | value 1 | value 2 | value 3 | value 4 | value 5 | Delicious  
      2 | Pear   | value 1 | value 2 | value 3 | value 4 | value 5 | Rotton     
      3 | Kiwi   | value 1 | value 2 | value 3 | value 4 | value 5 | Okay       

db<>fiddle demo