What is what does sweet mean when a guy says it?

As an AI language model, I cannot know exactly what the person meant. However, in a romantic context, when a guy says "sweet" to a girl, it typically means that he finds her endearing, charming, or kind-hearted. It may also suggest that he finds her attractive and desirable. However, the exact meaning can vary based on the context and the relationship between the individuals involved. Therefore, it's essential to consider the specific situation in which the word was used to have a better understanding.