SQL Server 2022

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

with T as (
  select *
  from (
  values ('Minesota Mining and   Manufacturing')
  , ('Minesota Mining & Manufacturing   ')
  , (' tillamook')
  , ('MUTUAL OF OMAHA')
  , ('   ')
  ) q(s)
),
scrubbed as (
  select T.s as InitialValue
  , CASE 
      WHEN LEN(RTRIM(T.s)) > 0
        THEN LTRIM(RTRIM(T.s))
    END as s
  from T
)
select s.InitialValue
, stuff(
    (
      SELECT ' ' + t2.word
      from (
          select str.value
          , upper(substring(str.value, 1, 1)) + 
            case when len(str.value) > 1 then lower(substring(str.value, 2, len(str.value) - 1)) else '' end as word
          , charindex(' ' + str.value + ' ', ' ' + s.s + ' ') as idx
          from string_split(s.s, ' ') str
        ) t2
      order by t2.idx
      FOR XML PATH('')
    ), 
    1, 
    1, 
    ''
  ) as INITCAP_attempt1
, convert(
      xml, 
      stuff(
        (
          SELECT ' ' + t2.word
          from (
              select str.value
              , upper(substring(str.value, 1, 1)) + 
                case when len(str.value) > 1 then lower(substring(str.value, 2, len(str.value) - 1)) else '' end as word
              , charindex(' ' + str.value + ' ', ' ' + s.s + ' ') as idx
              from string_split(s.s, ' ') str
            ) t2
          order by t2.idx
          FOR XML PATH('')
        ), 
        1, 
        1, 
        ''
      )
  ) as INITCAP_xml
, convert(
    varchar(max), 
    convert(
      xml, 
      stuff(
        (
          SELECT ' ' + t2.word
          from (
              select str.value
              , upper(substring(str.value, 1, 1)) + 
                case when len(str.value) > 1 then lower(substring(str.value, 2, len(str.value) - 1)) else '' end as word
              , charindex(' ' + str.value + ' ', ' ' + s.s + ' ') as idx
              from string_split(s.s, ' ') str
            ) t2
          order by t2.idx
          FOR XML PATH('')
        ), 
        1, 
        1, 
        ''
      )
    )
  ) as INITCAP_decoded
from scrubbed s

Data at the root level is invalid. Line 1, position 1.
   at System.Xml.XmlTextReaderImpl.Throw(Exception e)
   at System.Xml.XmlTextReaderImpl.ParseRootLevelWhitespace()
   at System.Xml.XmlTextReaderImpl.ParseDocumentContent()
   at System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace)
   at System.Xml.XmlDocument.Load(XmlReader reader)
   at System.Xml.XmlDocument.LoadXml(String xml)
   at ASP.index_aspx.PrettyXML(String XMLString)
   at ASP.index_aspx.__Render__control1(HtmlTextWriter __w, Control parameterContainer)