Can you drink expired Diet Coke?

My mom has been a huge Diet Coke fan for as long as I can remember. She also tends to stock up on Diet Coke when it is on a really good sale.

The only issue when your bulk buying Diet Coke is that it actually expires quicker than other sodas! Let’s take a deep dive into everything you need to know about expired Diet Coke and if you should drink it after it expires.

Does Diet Coke go bad?

Yes! Diet Coke can go bad, and it goes bad at a different rate than regular Coke. Typically Diet Coke in a can or bottle, needs to be consumed within 3 months of the expiration date.

How come regular coke can last up to 9 months, but diet cola only lasts 3 months? This comes down the sweeteners in both sodas. Let’s take a look at the ingredients for both sodas:

COKE: CARBONATED WATER, HIGH FRUCTOSE CORN SYRUP, CARAMEL COLOR, PHOSPHORIC ACID, NATURAL FLAVORS, CAFFEINE.

DIET COKE: Carbonated Water, Color (Caramel E150d), Acids(Citric Acid, Phosphoric Acid), Sweeteners (Aspartame, Acesulfame K), Natural Flavorings Including Caffeine, Acidity Regulator (Sodium Citrate).

Regular Coca Cola uses high fructose corn syrup which has a much longer shelf life and doesn’t degrade as fast. Diet Coke uses aspartame, and it actually starts to change its chemical composition over time.

For more information, check out “Is it bad to drink an expired Coke?“

The same ingredient that makes Diet Coke less calories is also why it expires so much quicker than regular Coke. As aspartame breaks down it changes chemically into aspartic acid, phenylalanine, and methanol.

This breakdown causes the soda to now taste sour, metallic, and bitter or even sickeningly overly sweet. To get technical, aspartame contains an ester element which causes it to breakdown instead of remaining stable like other sweeteners.

This same process happens in other diet sodas like Diet Dr Pepper, Coke Zero Sugar, and Diet Barq’s root beer.

Does expired Diet Coke taste different?

Yes! Diet Coke that has expired will have a noticeably different taste compared to fresh Diet Coke. The most common reaction is that it tastes sweeter and has a funky aftertaste.

Expired Diet Coke can also taste flat compared to fresh because overtime bottles and cans start to lose their CO2. Carbon dioxide is inside of soda containers to help keep the soda fresh and to prevent the growth of bacteria.

Once soda has passed the expiration date, the CO2 has lessened and causes a flat flavor. Some people describe this flatness as a loss of taste or even a slight bitterness and the liquid can become syrupy in texture.

How do you keep Diet Coke fresh?

The best way to keep Diet Coke fresh is to store it correctly. Unopened cans and bottles of diet coke need to be stored in a cool dry place like a pantry or cabinet. If you expect to drink it soon, go ahead and place it in the fridge.

There is some debate about if soda tastes different if it is stored cold and then stored in room temperature and then cooled again. Some people are very sensitive to this can notice a difference, others cannot tell at all.

Once a Diet Coke is opened, you will want to consume it within a few days. if you typically don’t finish a can in one setting, you may want to switch to small bottles.

Bottle of Diet Coke do lose their CO2 quicker than cans, so the freshest Diet Coke will mostly likely be found in cans.

Ideally, you will want to store cans in a pantry, and then place them in the fridge long enough to be cold before drinking.

How long does Diet Coke take to go flat?

In general, Diet Coke should not go flat before the expiration date unless that can or bottle is damaged. If the container is undamaged, then it usually will take more than 3 months to go flat if it is also unopened.

The only problem here is that after 3 months, the artificial sweetener will degrade and will make the soda taste awful. So, does it really matter if the soda is flat if it is going to taste bad?

How long after the expiration date can you drink Diet Coke?

You can safely drink an unopened can or bottle of Diet Coke up to 3 months after the expiration date. If the container has been damaged or punctured, you will want to toss it.

Another sign of damage to a can of Diet Coke is a bulging top or bottom. This is a good indicator that the liquid inside has gotten too cold. Once the can has bulges, it can become affected by air and possibly start to grow bacteria.

A can that is undamaged is unlikely to grow bacteria or mold due to the CO2 inside the can. Even if the can is way past the expiration date, the likelihood of growing mold and bacteria is slim until the liquid is exposed to oxygen.

If you love Diet Coke and see a really good deal on it, go ahead and stock up! Just be mindful of the expiration date. Most cans will have a “best by” date of about 6-9 months from purchase.

Ideally, you will need to calculate how many Diet Cokes you will typically consume in this available time period. If you most likely will not finish them within 3 months of the expiration date, then consider buying less.

For more information about expired foods, check out “Can I eat expired Pirate Booty (Puff Corn)?” and “Can you eat old Hamburger Helper?“