Bash' code to store string of any characters containing pair of "" and '' at once

[Budi]

How is Bash' code to store string of any characters should be containing
pair of "" and '' at the same time explicitly, being exact verbatim so,
ie. cannot be modified, escaped or etc, as expected from ordinary/naive
human writing), into a variable
let, eg., it be

*foo "foo" and 'bar' content*

v="$(echo foo "foo" and 'bar' content)"
v=$'foo "foo" and 'bar' content'

...
so on its combination up >7 tries to no avail.. so help out solve