Over the past year or so, we've truly witnessed a revival of Diet Coke — a Renaissance, if you will. Fellow DC lovers (nope, not the comics) are probably familiar with the social media craze and even "recipes" for elevating everyone's favorite afternoon pick-me-up. The peak really hit in 2023, when it became impossible to escape the videos of someone opening a can of crispy Diet Coke, dumping in a packet of crystallized lime juice, and stirring it around with a glass straw before taking that satisfying first sip.
Personally, I've always been a Coke Zero gal through and through (and you know what? I might still be), but the Diet Coke girlies definitely got to me. Before I knew it, cracking open a 2 p.m. Diet Coke in the office became somewhat of a ritual that I always looked forward to. Then something tragic happened: Caffeinated sodas began disappearing from our fridge, and yes, that included my beloved Diet Coke.
After simultaneously witnessing all the Diet Coke discourse on my feed and chatting with my coworkers about our mutual sadness over no longer having it, I realized that we all take this beverage very seriously. Specifically, people tend to have strong opinions when it comes to the different vessels Diet Coke comes in: bottles, cans, fountains, etc.
Cans tend to take over my feed, but I often hear people's preference for McDonald's fountain Coke/Diet Coke in particular. So as someone very interested in seemingly pointless data, I needed to know once and for all which one ranks supreme, and whether any of us can even tell the difference among these.
So with the incredible help of my coworker Ross, I set out to conduct an office-wide blind taste test with four types of Diet Coke: in a plastic bottle, a glass bottle, and a can, as well as one from the McDonald's fountain.
Each Diet Coke was assigned a number and then poured into 3-ounce cups, which we labeled. Our testers were then asked to try the Diet Cokes one by one, guess which container it came in, and give a final ranking from their favorite to least favorite.
Before we dive into the results, we need to have a chat about McDonald's. McDonald's Diet Coke is usually seen as top tier, and per their own website's FAQ section, this is why: "The water and Coca-Cola syrup are pre-chilled before entering our fountain dispensers with the ratio of syrup set to allow for ice to melt." Not going to lie, this kind of blew my mind. I always knew that McDonald's made Coke the "traditional" way, using syrups, but never knew they considered how ice would dilute the drink.
They also use filtered water, and of course, there's the straw, which is "wider than a typical straw so all that Coke taste can hit your taste buds."
With all that Diet Coke science in mind, we came up with a McDonald's plan. First, order two large Diet Cokes with no ice (I messed this up the first time, oops). Second, dilute the Diet Coke with about 1 ounce of water to replicate the dilution from melted ice. Last, pour it into SodaStream bottles to prevent it from going flat.
While the SodaStream bottles were meant to keep in the bubbles, we definitely ran into some issues. I picked up the sodas in the morning, and they immediately looked flat as I was pouring, so I had little hope for how they'd hold up. I also realized I definitely needed more. Now, worried that 1) we wouldn't have enough Diet Coke and 2) our taste test would be thrown off by flat soda, I went to a different McDonald's and grabbed two more. Again, they were flat.
During our taste test, we came to the conclusion that we couldn't justify serving soda that was this flat. So, again, we grabbed two more Diet Cokes from yet another McDonald's (Times Square is definitely not short on them). This location was a little more fizzy than the first two (and served to our remaining testers almost immediately), but it still didn't seem to change people's opinions about the McD's Diet Coke.
Whew, what an emotional roller coaster. With our McDonald's fiasco finally settled, here is our official Diet Coke ranking from worst to best.
4. McDonald's Fountain
Not only did our testers have an issue with McDonald's Diet Coke being flat, but they also found it to be overly sweet. One noted that they "could taste the fountain syrup," and someone else thought it could be mistaken for regular Coke because of how sweet it was. We even had someone describe it as "bouba" (I won't get into the kiki-bouba effect, but it was probably the most accurate description I'd heard all day).
The "syrupy" flavor was likely a dead giveaway, since a majority of the testers accurately guessed that this was McDonald's. However, the lack of fizz made many of us think this was one of the other three; no one expected McD's to be the flattest of the bunch. If anything, we all thought it would have some of the best fizziness. Alas, we were left disappointed.
⭐️ OVERALL RATING: 1.5/5
3. Glass Bottle
A few of our testers thought it had that "classic" Diet Coke taste. Some thought the flavor was flat, and when it came to fizziness, they were split. Some found it to have a good fizz, while others thought it was flatter or even watered down. Personally, I found the fizziness to have a nice middle ground: It was fizzy without weirdly hurting your nose from being over-carbonated. But I definitely understand that it didn't meet everyone's bubbly Diet Coke expectations.
Funnily enough, half of our testers thought this was the plastic bottle. My guess is that plastic bottles are thought to be a little less fizzy, plus the glass bottle still had the "classic" taste most people expected. It's also unsurprising, given that glass bottles aren't always the easiest to find (petition to change this, please), so people are a little less familiar with the taste.
⭐️ OVERALL RATING: 3.2/5
2. Plastic Bottle
Most of the testers thought there was a nice level of fizziness, and again, a few recognized the classic Diet Coke flavor. One person described the flavor as "smooth and light," and I'd have to agree. I definitely found it to have a lighter flavor than the others (especially McDonald's...), although some people pointed out that it was a little sweet.
Guesses were pretty split, but a majority still thought this was a glass bottle, even yours truly. I think the "lighter" flavor, combined with a decent level of fizziness, fooled a lot of us into thinking it was in a higher-quality container. This, again, is pretty fascinating, considering that people would normally rank a plastic bottle at the bottom of their list.
⭐️ OVERALL RATING: 3.8/5
"Main character energy," "summery," "crisp" — yeah, this was definitely a favorite. The fizziness from the can really smacks you in the face, and despite having been in an open container that couldn't be resealed between testers, it didn't lose its fizz. Whereas McDonald's was "bouba," the canned Diet Coke was aptly described as "kiki." I took one sip and immediately said, "Whoa, zigzaggy." And if none of those adjectives means anything to you, think of it as the one you'd want to pour over ice with a little lime on a hot summer day.
Even though guesses were still relatively split, most people guessed this was the can. One tester literally took one sip and said, "Yup, that's a can" — it was very impressive. This is likely what Diet Coke connoisseurs often reach for, especially since it's what's readily available in offices, restaurants, delis, planes, etc.
⭐️ OVERALL RATING: 4.4/5
So, yes, canned Diet Coke technically won and was certainly tied with McDonald's when it comes to ease of recognition. But (and this is a very big but) I'm hesitant to declare it the supreme Diet Coke. With the exception of McDonald's — which clearly ran into some mishaps — there wasn't a definitive consensus for each Diet Coke.
All in all, the main takeaway I got from this taste test was that whatever you choose to drink your Diet Coke out of is really personal preference. Case in point: I will always reach for a glass bottle over a can because I like a medium-level fizz plus crisp flavor.
And will I ever pass up a McDonald's Diet Coke when I'm in the middle of a road trip and deserve a fun treat? Absolutely not.
Let us know which is your favorite Diet Coke in the comments! Or maybe there's a secret fifth option we need to try next.