;with TableA (ID, JunkData) as
(
       select 1, '1234jdueakj34jfjj4' union all
       select 2, '345j5uttuvj5575jkf' union all
       select 3, 'sjhsdfk283ncfkjsf9'
)

select a.ID
       ,substring(a.junkData, n.number+1, 5) [SplitData5]
from   TableA a
join   master..spt_values n
       on n.type = 'P'
       and n.number % 5 = 0
where  n.number < len(a.junkData)


OUTPUT:
ID          SplitData5
----------- ----------
1           1234j
1           dueak
1           j34jf
1           jj4
2           345j5
2           uttuv
2           j5575
2           jkf
3           sjhsd
3           fk283
3           ncfkj
3           sf9