The Sugar Free Imperial Fizz (aka the Whiskey Fizz), is a slight twist on the regular recipe. Normally, light rum is not included at all, but we found this variation on Drinksmixer, which we thought really added a nice nuance of fruitiness to the drink.
The Sugar Free Imperial Fizz can also be found in our favorite go-to recipe book, the Savoy. (Actually, this recipe also agrees with Drinksmixer). There is also an alternate recipe that substitutes blended whiskey for a single malt scotch and the rum for a spiced rum. It sounds delicious, though maybe not as light of a cocktail since the flavor profiles would be a bit stronger. Definitely something worth exploring, though.
The Savoy Stomp has several alternate versions listed. Very, very intriguing…
The Sugar Free Imperial Fizz
Just add the rum, whiskey, realemon and splenda over ice in a shaker bottom, cap, and give it a good shake. Strain out the ice and pour into a double old fashioned glass. Top off with some soda water and enjoy!