A good friend of mine, Cindy Plant, makes it very clear that anyone eating the lollies on the table must enter into a contract to sustain their intake for the rest of the day. She does not want to be dealing with grumpiness or aberrant behaviour when people come down from their sugar induced high.
The consumption of alcohol in small quantities may be 'social' in some settings. If you are facilitating, take a page from Cindy's book, and let people know what you expect from them. This also counts for 'the next morning' effects of alcohol consumption.