Alcohol has a complicated effect. The liver normally helps keep blood sugar steady, but while it is processing alcohol it does this less effectively, which can lead to lower blood sugar, sometimes delayed for several hours, including overnight. For people on insulin or sulfonylurea-type medicines, this increases hypo risk.
At the same time, sweet drinks, liqueurs, and sugary mixers can raise blood sugar, so the overall effect depends on what and how much you drink. Hypo symptoms can also be mistaken for drunkenness, which is a safety concern.
If you have diabetes and choose to drink, general advice includes not drinking on an empty stomach, eating carbohydrate alongside alcohol, and checking your blood sugar, including before bed. Discuss safe limits with your doctor, particularly given any medications you take and your local health guidance.