I'm a firm believer in the idea that drinks have personality. Whether lone spirits or mixes, potables have idiosyncratic qualities just like people. As such, a lot of my opinions about drinks have more to do with whether or not I like them as people than how they actually taste. Take absinthe, for instance. I'm not a fan of the flavor of anise but I don't have many disparaging things to say about the green fairy. It does what it's supposed to do and doesn't apologize for its quirkiness. Like a man who's too old to change his ways, absinthe dresses, talks and believes how and what it wants, modern conventions be damned. I have a great amount of respect for the martini for being both bold and refined, a long-lived professional of a cocktail that continues to be the sharpest guy in the room without doing anything flashy. So, when I say that I both love and fear the rum and cola, know that it comes from a place of both experience and contemplation.
First of all, I'm of the opinion that the mix shouldn't be called by its brand name, Rum and Coke. If Coca-Cola was somehow irreplaceable in the recipe I'd feel different but there's no real reason why it has to be one kind of cola or another. The point of rum and cola is to use the syrupy sweetness of the soda to alleviate the burn of the rum. And honestly, the distinct flavors of the rum itself tend to cover up any minor notes that distinguish one cola from another. Really, that's a big part of why rum and cola is a sinister drink. First, it basically makes a potent cocktail out of something that tastes like a rum-flavored soft drink. Second, the lack of appreciable taste difference makes the rum and cola one of the cheapest cocktails imaginable because the two strongest flavors in it can be achieved with the least expensive ingredients possible. Is there a difference between a top-shelf rum mixed with Coke Classic and a well rum mixed with generic store-brand cola? Maybe, just not enough to matter. Cheap cocktails incentivize mass consumption, ergo drunkenness.
All of the above makes rum and cola unbelievably easy to drink, but there's another layer beyond how pleasant it is to just swallow the stuff. Unless you're using caffeine-free cola, your cocktail has the rare opportunity to hit your body with both a depressant and a stimulant simultaneously. Unfortunately (or fortunately) the two psychoactive components of the drink don't compete or cancel each other out. Rather, they work together to have mostly separate but equal effects. The alcohol does its usual work of lowering inhibitions, reducing nerve uptake and slowing cognition while the caffeine keeps the drinker awake, jittery and, most importantly, pursuing more stimulants. In short, it's addictive behavior minus a superego.
I personally witnessed the ugly side of the rum and soda in my early days as a bartender. Working the late shift at a dive, one of my regulars made it a habit of knocking back Captain Morgan and Coke like it was... well, exactly what it is: A sweet, deceptively potent cocktail without the prohibitive burn of liquor. Whether it resulted in him dropping glasses and stumbling home come last call or picking fights with patrons and staff, this rum and cola enthusiast ended every night in the saddest states of alcoholism. Was the rum and cola to blame for his addiction? Absolutely not, but it did let him drink more and longer than other cocktails would have. I enjoy the drink and I'd recommend it to anyone who enjoys the ingredients, but that recommendation comes with a word of caution. Rum and cola is a dangerous drink.