The way I work this is:

Declare

@CrLf char (2)

SET @CrLf = char(13) + char(10)

select @cmdtxt = "echo "+ @string1_to_write + @CrLf + @string2_to_write + @CrLf" >> c:\temp\myfile.txt"

I had a rough time with this at first because I tried to reverse the CRLF sequence which does NOT work. When you open your file in a "pure" text editor like NotePad, you'll have what you expect to find.

Butch