I think Honoka means that Kotori smells like sweets because she's thinking about food while Umi is thinking about how Kotori smells good in a more sensual way.
Or, alternatively, it's a lost in translation joke where maybe "sweets" sound similar or sounds like another word for something more explicit.
Kinda reminds me of the thing, uhh HoriMiya manga with Miyamura's friend that hates cheese and Miyamura knows that and says, "say Ahhh~" to that guy feeding him a cheese lolly. I feel sorry for You now xD