The term "spiced up" means to add excitement, interest, or variety to something. Therefore, its antonyms signify its opposite meaning. The first antonym is "boring," which means unpleasantly dull, repetitive or not engaging. The second antonym for "spiced up" is "mundane" which means lacking excitement or interest, monotonous or ordinary. The third antonym would be "unadorned," which means plain or dull. The fourth antonym is "uneventful," which means not involving any exciting or remarkable events. Lastly, "unchallenging" is another antonym for "spiced up," which means not presenting any difficulty or challenge, unexciting or undemanding. All of these antonyms oppose the idea of adding excitement and interest to any situation or object.