The idiom "guilty pleasure" is used to describe something that you enjoy doing or consuming, but feel a little bit ashamed or embarrassed about. It's something that you might not want to admit to others that you like, because you know it's not considered cool or socially acceptable.
For example, if you secretly love watching reality TV shows, but you know that your friends think they're trashy and lowbrow, you might say that watching those shows is your "guilty pleasure." Or if you have a weakness for junk food, but you know that you should be eating healthier, you might say that eating those foods is your "guilty pleasure."
The term "guilty pleasure" implies that there's a sense of guilt or shame associated with the activity or item in question, but that you still can't help enjoying it. It's a way of acknowledging that you know something might not be the best thing for you, but you still find it enjoyable anyway.
• My guilty pleasure is eating chocolate every day.
• Watching reality TV shows is my guilty pleasure when I need to relax.
• I know it's not healthy, but my guilty pleasure is spending money on designer clothes.
• Going to the beach and getting a massage is my guilty pleasure, even though I know it's a luxury.
• Listening to pop music is my guilty pleasure, even though I pretend to like indie rock.
• My guilty pleasure is reading cheesy romance novels, even though I'm a literature professor.