I had insomnia with exemestane.
I was on Anastrazole first (lasted a couple of months before being changed) and had it 5 days out of 7. Exemestane (on for 6 months) was 3 days out of 7. It happened no matter how tired I was before bed - a twitch or a snore from himself would jerk me awake and that was that
I coped with using my kindle (no need to put on the light to read) and usually fell asleep about 3am
Please remember I am only talking of my own experience here as we all seem to suffer a pick and mix of side effects