After all details, it means, that no reasons to use $lb, or any other ways, it should be as is as a string, but with this length's header.

In Cache, we don't have binary strings as do other languages, but what is a byte, it is a symbol for text, so text will be arrays of bytes.

write $c(166, 70, 114, 105, 110, 103, 101)
¦Fringe

The only thing you should care as already mentioned above is different codepages. 

Let's try for some example:

And try to get the same.

USER>set data="TestТест"
 
USER>zzdump data
 
0000: 0054 0065 0073 0074 0422 0435 0441 0442                 TestТест

USER>set msg=$zcvt(data,"O","UTF8") ; convert from Unicode
 
USER>set msg=$c(160+$l(msg))_msg    ; of course should be changed for bigger text
 
USER>zzdump msg
 
0000: AC 54 65 73 74 D0 A2 D0 B5 D1 81 D1 82                  ¬TestТеÑ.Ñ.

and as you can see we got the same result

I love Docker way. In Dev environment, when you need only some test data. You can use Docker, with all test data inside the image, just recreate container will clean all previous changes and return the database to state when this image was built. If you later will decide to keep some changes as default for next uses, you can commit this changes to the image.