@bimbra and @scottrl
I thought this was a very interesting question, so I did a little looking - it actually seems the opposite is true - smelling food can release insulin, and should cause blood glucose to fall.
Here is an article about it:
https://www.diabetesselfmanagement.com/education/blood-sugar-management/blood-sugar-and-food-smells-diabetes-questions-answers/
On the other hand, hunger can cause blood sugar to spike, so if you need to eat, but don't, for example when a craving hits or near mealtime, your body releases extra glucose.