How to assign GUID to batches of data based on row counts and tunable batch size
you have to play with row_numbers
 declare @part int = 3
 
 ;with baseRowNums as 
  (
    SELECT ID, VALUE1, VALUE2,
       Row_Number() Over (ORDER BY ID) AS rn
    FROM BASE_TABLE
  )
 ,batchNums as
 (
 SELECT *,
    Sum(CASE WHEN rn % @part = 1 THEN 1 ELSE 0 END)
    Over (ORDER BY ID, rn 
          ROWS Unbounded Preceding) AS part
 FROM baseRowNums
 )
 ,GUIDs as
 (select part, MAX(newid()) as GUID
  from batchNums
  group by part
 )
 select ID, VALUE1, VALUE2, GUIDs.GUID
 from batchNums
 join GUIDs on batchNums.part = GUIDs.part

https://dbfiddle.uk/?rdbms=sqlserver_2019&amp;fiddle=7c26d9bab095ce9d8ca1abf1f4c1a898