I'd do food, it would be easier to mask the taste with a variety of flavors rather than just one. Sleeping pills will have a slightly bitter taste, especially when ground up. If someone drinks something that tastes a little off they'd be more suspicious than if the food tastes off. Wine should never taste bad unless someone added something to it, but food can have a large variety of reasons for tasting a little strange. Also you can add more sedatives to food compared to wine, as people would be more particular on the taste of wine, so you'd need to get the character to drink a few glasses of wine each just to get the same effect as each of them having a full meal. Personally though, there are more efficient ways to drug a person than sleeping pills, as you'd need a decent amount of them. But, I don't know your story, and in a pinch, sleeping pills will work just fine. Hope that helps.