Here "wickedness is sweet" represents a person enjoying doing wicked things. Alternate translation: "Although doing wicked things is pleasurable like tasting sweet food in the mouth" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Zophar speaks of wickedness as if it were sweet food that a person puts under his tongue so it will stay in his mouth and he can taste it for a long time. (See: [[rc://en/ta/man/translate/figs-metaphor]])