When I was in Korea I found a bar that had grape juice. I would order vodka and grape juice and it tested like grape soda, except that it was flat. Since then I have given up drinking alcohol and shortly after a product called SodaStream came to market. If vodka can be carbonized that would be a great solution to the flatness of the drink.
If anyone reading this likes alcohol, and has access to a SodaStream, please try this and let me know if it works. I want to know but I don't care enough to start drinking again.