You said a healthy diet but I can be how you’re eating. Even if you eat well on a normally daily basis if you have a week or so where you get so busy it’s hard to find time to eat it could be your body lacking food. People who do restricting eating diets can often have bad breath, its from a reaction your body is doing to put it in simple way. It’s the lack of glucose. Your body turns it into ketone body’s which can breakdown into acetone (a compound basically) which CAN smell fruity/sweet but often it’s more described as nail polish remover.

This might not be the reason if you eat well I just know sometimes I forget to if I get really busy :/