What effect will drinking alcohol have on my diabetes control?

Depends: Depends on the alcohol. If it is drinking beer and wine then it will adversely affect your blood sugar. If you are speaking of a distilled beverage with no mixer other than water or carbonated water it will have no effect on your glycemic index.

Multiple Effects: First is any carbs in the alcoholic beverage. Beer, wines, and margaritas have quite a bit; scotch & soda has none. Second is the effect of the alcohol on food consumed. Many people find it harder to stick to a meal plan after drinking; this can lead to higher sugars. Third is a decrease in production of glucose by the liver when the liver is busy detoxifying the alcohol. 1-2 servings only!