declare @sql varchar(100)
declare @cr char(1)
declare @nl char(1)
set @cr = char(13)
set @nl = char(10)
set @sql = 
'print 1'          + @cr + @nl + 
'/* Comment one */'  + @cr + 
'print 2'          + @cr + @nl + 
'/* Comment two*/'   + @cr + @nl + 
'print 3'          + @cr + @nl + 
'/* Comment three*/'       + @nl +
'print 4'

print '
What you see...'
print '-----------------------'
print @sql
print '
is not what you get!'
print '-----------------------'
exec (@sql)

set @sql = 
'print 1
-- Comment one print 2
-- Comment two
print 3
-- Comment three
print 4
'
exec (@sql)