Over the course of a few hours of drinking, your liver is busy getting rid of alcohol, so can't continue the drip feeding of glucose into your blood stream. As a result, after a few hours of drinking you will notice a moderate drop in your sugar levels. Not a massive drop, but a gradual one.
Conversely, beer or non-diet mixers will raise your levels. The best drinks to maintain fairly static sugar levels are dry whites, any reds or diet mixers with spirits.
Of course, this is assuming you manage your levels well whilst eating out. Typically, this isn't easy, so I'd suggest you go for something with the fewest carbs in and drink drinks with the fewest carbs in. The fewer cabs, the easier your control will be.