Difficult to find a definitive ingredients list, but it appears to contain 10 calories per can and only drinks which contain 1 calorie per glass are recommended. It also seems to include a carbohydrate called glucuronolactone.
I used to drink sf red bull quite a lot whilst in the car on long journeys, but I haven't needed it all since starting the diet. There's almost always a can of diet coke around though.