Chocolate affect 2 year old sleep?

[FairRoseFox]

My just turned 2 year old has a pretty good diet and sleeps reasonably well (although previously terrible). I never buy her chocolate, however when she has had chocolate (e.g birthday cake, nan has given a chocolate biscuit or yesterday she ate a chocolate topped rice cake that has been left on table) her sleep is awful and awake all night. My husband thinks it's a coincidence but genuinly its every time. I remember because she so rarely has chocolate and usually sleeps well.
Nothing on Google suggests a link either?

Well chocolate is a mild stimulant but in such a small amount I don’t know if it would have an impact on sleep.
Obviously not the rice cake but could it be linked more to the event or occasion? She could be over stimulated after a party for example and struggle to calm enough to sleep.