We walk in the dark places no others will enter
We stand on the bridge and no one may pass

DECLARE @Test   VARCHAR(MAX),
        @String VARCHAR(MAX)

 SELECT @Test = '',
        @String = '1234567890'

;WITH
cteTally AS
(--==== Create a Tally CTE from 1 to 10,000
 SELECT TOP (10000)
        ROW_NUMBER() OVER (ORDER BY t1.ID) AS N
   FROM Master.sys.SysColumns t1
  CROSS JOIN Master.sys.SysColumns t2
)
 SELECT @Test = @Test + '1234567890'
   FROM cteTally 

 SELECT LEN(@Test)

We walk in the dark places no others will enter
We stand on the bridge and no one may pass