Perhaps why its called phenomenon, something that occurs out of the ordinary and may vary per individual, where in your case one drink at bedtime raises your
glucose levels. This may be caused by the sugar in
alcohol, little as it may be its still present.
The jury is still out on DP and there's a lot of psuedo scientific material on the net. Mendosa, who has positive reports,
http://www.mendosa.com/blog/?p=232 , says the opposite, that it lowers. So who knows?