How might Twelfth Night be considered a satire of sentimentality?

Love is the central concern of Twelfth Night, and most of the characters indulge in sentimentality at one time or another. The overall satirical stance is conveyed early on by Duke Orsino, as he listens to music and sighs while daydreaming about love: “If music be the food of love, play on;/ Give me excess of it.” His intention to over-indulge in love and the things that nurture it is a common attitude of other lovers in the play. Orsino’s supposedly deep love, which shifts rapidly, indicates that it is the idea of love that he actually enjoys the most. Olivia, originally the object of his desire, is similar in temperament, and her affections are also transferred quickly to another man.
The pairing up of the main couples by the end is achieved through a series of deceptive steps, including gendered disguises. Viola, the most level headed of the four, mocks constancy in love by defending it while actually pretending to be someone else, a man.
Another satirical aspect is presented by the plot in which Malvolio is fooled into believing that he is the object of Olivia’s love. He is so swayed by the idea of her adoration that he is willing to make a complete fool of himself by dressing in exaggerated fashion just because he thinks she likes that style. Excessive sentiment causes him to throw reason out the window.