I would either take right before sleep with a snack or, (preferably), as soon as I wake with a snack. Mainly because I never take anything on an empty stomach due to previously having had gastritis. It does work quickly so you could take as soon as you wake, lie in bed and do some breathing, and then in 30 mins you should be feeling the effects. I have not found it lasts all night tbh and the one time I did take in the evening, it impacted my sleep. However we are all different.
Suffice to say it doesn't really matter from a clinical point of view, so just find out what works best for you from a symptom point of view.