What is the meaning of Sweeten?

To make sweet to the taste.

To make (more) pleasant or to the mind or feelings.

To make mild or kind; to soften.

To make less painful or laborious; to relieve.

To soften to the eye; to make delicate.

To make pure and healthful by destroying noxious matter.

To make warm and fertile.

To raise the pH of (a soil) by adding alkali.

To restore to purity; to free from taint.

To make more attractive; said of offers in negotiations.

To become sweet.

To supplement (a composition) with additional instruments, especially strings.

Source: wiktionary.org