What a grape, err I mean great, costume idea! It may not be a pet-safe snack, but it's a neat ensemble nonetheless.
Turn your own dog into Grapes on a Vine . . . on a dime! OK, more than $.10 but this costume can easily be had, especially if your pup already has a green coat or sweatshirt.

To create, simply blow up purple balloons (or choose red or green balloons for your favorite flavor) and hot glue them to the coat. Add on some leaves cut from a garland and you've got a fine costume on your hands — just be sure to place the balloons where your pup can't accidentally pop them and put it out of reach when the photo opp's done.

Source: Flickr User thenestor