Here "wickedness is sweet" represents a person enjoying doing wicked things. AT: "Although doing wicked things is pleasurable like tasting sweet food in the mouth" (See: [[rc://en/ta/man/translate/figs-metaphor]])
# although he hides ... does not let it go
This represents wanting to continue to enjoy the wickedness as one wants to continue enjoying tasty food by keeping it in the mouth. (See: [[rc://en/ta/man/translate/figs-metaphor]])