I believe the problem is probably more the sugar or corn syrup, which is the main ingredient of the chocolate syrup, that keeps you awake. Add some chocolate with caffeine to that and its not a good bedtime drink. I used to give my kids what I called “Duck Milk”, which was warmed milk with honey in it at bedtime and believe it did somewhat induce sleep.

Maybe, if you have developed a sensitivity to caffeine.

I like to put a tiny blip of brandy in my own bedtime glass of milk. Mmmmmmzzzzzzzz. No sugar, no choc.

Four tablespoons is an awful lot of syrup. I would expect the HFS to have more of an effect that the chocolate (which may not even be genuine).

Another psychoactive stimulant in cocoa solids (a main ingredient of chocolate syrup) besides caffeine is theobromine. But I don’t know what the concentrations of either are.

I’ve been partial to chocolate milk at bedtime too, but I’m not super sensitive to caffeine until the dosage gets up into the large cuppa black coffee range. However, I have noticed a tendency to develop diarrhea when I do indulge in this.

More likely the sugar in that’s keeping you up than the caffeine.