It seems that Varys and his Little Birds attempted to poison Daenerys
If you were anything like us while watching the latest 'Game of Thrones', you were so preoccupied with the imminent Battle of King's Landing that you may have missed an important scene at the beginning.
An early scene of 'The Bells' sees Varys in his room when one of his 'little birds' - a kitchen girl called Martha - comes in to give him a message. The conversation seems either a little confusing or irrelevant, so we didn't properly register what was said, but here's a recap:
Varys: “Nothing?”
Girl: “She won’t eat.”
Varys: “We’ll try again at supper.”
Girl: “I think they’re watching me.”
Varys: “Who?”
Girl: “Her soldiers.”
Varys: “Of course they are, that’s their job. What have I told you, Martha?”
Girl: “The bigger the risk, the bigger the reward.”
Varys: “Go on. They’ll be missing you in the kitchen.”
In short, it appears that Varys was attempting to poison Daenerys, who scuppered his plan by not having an appetite.
It also harkens back to a conversation that Ned Stark had with Grand Maester Pycelle in Season 1, which saw Ned claim that poison is "a woman's weapon". Pycelle then replies "Yes. Women, cravens... and eunuchs."
It doesn't change the story in any major way, but it does make his execution for treason a little easier to justify on Dany's part. That's if you can ever justify killing someone by dragonfire, of course.