Note that you might replace strings you don't want them to be replaced.

INSERT INTO @test-2(TEST_STRING)

VALUES

('I am a bad Gal')

,('I am a good Gal')

,('Oh my goodness! There''s no more goodwill')

,('He''s a patient with Osgood–Schlatter disease');

SELECT

*, REPLACE(TEST_STRING, 'good', 'bad')

FROM @test-2 T

WHERE T.TEST_STRING LIKE '%good%';