How to Tell If a Soft Drink Has Gone Bad? 15 Key Signs
Ever cracked open a soda and thought, “Wait; does this smell weird?” You’re not alone. A soft drink can look fine but still be spoiled. If you’ve ever wondered how to tell if a soft drink has gone bad, I’ve been there too—and I’ve got answers.
Sour smells, floating stuff, flat taste, and even fizzing before you open it are all signs something’s wrong. The truth is, a spoiled soda can give itself away if you know what to look for.
In this post, I’ll walk you through every single sign I’ve personally seen.
How to Tell If a Soft Drink Has Gone Bad? (Signs of Spoilage)
A soft drink has gone bad if it smells strange, tastes flat, has no fizz, looks cloudy, or changes color. I always check these signs before drinking soda, especially if it’s been sitting around for a while.
Here’s a table on all the signs of spoilage of a soft drink:
| Sign | What It Means |
| Flat taste | Lost fizz, tastes dull or syrupy |
| No carbonation | No hiss or bubbles when opened |
| Off smell | Sour, musty, or unusual odor |
| Cloudiness | Drink looks hazy or foggy |
| Changed color | Looks darker or different than normal |
| Mold or particles | Floating bits or mold near cap or surface |
| Bulging can or bottle | Swollen container from gas build-up |
| Leaking or sticky packaging | Seal may be broken or pressure is escaping |
| Unusual taste | Bitter, sour, metallic, or overly sweet |
| Past expiration date | Higher chance of spoilage after this point |
| Broken seal | Cap is loose or tampered with |
| Fizzing before opening | Bubbles inside while still sealed |
| Rust or corrosion on cap | Poor storage, possible contamination |
| Sticky lid area | Signs of leakage or pressure |
| Weird pressure on opening | Either no fizz or too much fizz |
Flat taste means the soda has lost its fizz and tastes dull
When a soft drink goes flat, it just tastes off. The bubbles are gone, and the flavor feels weak. I’ve had this happen when I left a can open overnight. The next day, it tasted more like sugar water than soda.
Flat soda isn’t unsafe most of the time, but it doesn’t taste good. It feels thick and syrupy in your mouth.
I’ve noticed this happens faster with clear sodas. Lemon-lime drinks tend to go flat sooner than cola. That’s why I try to finish those quickly.
No carbonation means there’s no fizz or sound when you open it
If your soft drink makes no fizzing sound when you open it, it has likely gone bad. This has happened to me when I’ve left a bottle in the fridge for too long after opening it. I’ve also had it happen with unopened drinks that were stored in warm places.
I’ve learned to check by gently tilting the bottle before opening. If I don’t see bubbles clinging to the inside, I already know it’s probably lost its fizz. And when that happens, I skip it.
Off smell means the soda may be spoiled or contaminated
The author at “Energy Beverages: Content and Safety” says that a bad smell is a strong sign the soft drink is no longer safe to drink. I once opened a can of orange soda that smelled sharp and sour. It reminded me of vinegar. I didn’t take a sip. That smell told me all I needed to know. Soda isn’t supposed to smell like that.
A spoiled soft drink, like diet Coca Cola, might smell sour, musty, or chemical-like. Sometimes the change is obvious. Other times it’s more subtle, but still enough to make you pause. I’ve had clear sodas that smelled like plastic. That’s not normal.
Cloudiness means the soda is no longer fresh or clean
Cloudiness can be a sign of contamination or spoilage. I’ve heard that it can happen if bacteria starts to grow, especially if the drink was left open too long. USDA states that it can also happen if the soda was exposed to heat or light, which breaks down the ingredients.
I usually see this with clear sodas like Sprite or ginger ale. If they start to look milky or murky, I know not to trust them.
Changed color means the soda has likely gone bad
If your soda looks darker or has an unusual color, it’s probably expired or spoiled. Color changes happen when the drink has been stored for too long or exposed to heat.
I’ve seen lemon-lime drinks turn yellowish. I’ve seen cola go darker and look thicker than usual. It’s always a clear sign something’s wrong.
Mold or particles mean the drink is no longer safe to consume
If you see floating bits, sediment, or mold near the cap or inside the drink, it’s gone bad. Particles and mold usually show up when a soft drink has been open for too long or wasn’t sealed properly. Sometimes, it happens with old drinks that have passed their shelf life.
Even if it smells okay or still has fizz, visible stuff floating in the drink is a clear sign to stop. I never drink a soda if I see anything strange inside.
Bulging can or bottle means there’s pressure from gas buildup
If the can or bottle looks swollen, don’t open it. I once picked up a soda can that felt bloated. The top was puffed out, and the sides were rounded. I didn’t even bother opening it. That kind of pressure usually means gas has built up inside. And that gas can come from bacteria that’s started to grow in the drink.
Leaking or sticky packaging means the seal may be broken
According to the Trends in Beverage Packaging, if the outside of a can or bottle feels sticky, the drink may not be safe. I once found a soda bottle at the back of my fridge with a sticky ring around the cap. It hadn’t spilled, but the seal was broken. When I opened it, the fizz was weak, and the smell was off.
A soft drink that’s sealed properly shouldn’t feel sticky on the outside. If it does, or if you see dried soda around the cap, don’t drink it.
Unusual taste means something has changed in the drink
If your soft drink tastes bitter, sour, metallic, or extra sweet, it may be spoiled.
I’ve had this happen a few times. I took a sip of cola and noticed a sharp sour taste that wasn’t normal. Another time, a ginger ale had this weird metallic flavor. Both times, I knew something had changed, even if the drink still looked fine.
Past expiration date raises the chance the soda has gone bad
If your soft drink is past its expiration date, check it closely before drinking. The expiration date on soft drinks is there for a reason. It’s the manufacturer’s way of saying, “We can’t promise quality after this point.”
Past that date, the soda , like Pepsi, may lose carbonation, flavor, or even start to spoil, especially if it wasn’t stored right.
Unsealed or broken seal means the drink might be unsafe to drink
If the seal on the bottle or can is broken or looks tampered with, don’t drink it.
One time, I bought a bottle that had a loose cap. It didn’t give that tight crack when I opened it. I knew right away something was wrong. The soda inside was flat, and the taste was off.
According to the LWT Volume 43, the seal on a soft drink keeps air and bacteria out. If that seal is damaged, the drink is no longer protected.
Fizzing before opening means there could be bacterial activity inside
Fizzing before opening can be a sign of fermentation. That means bacteria might be inside the drink, creating gas and pressure. It’s the same reason bread dough rises, but in a sealed soda bottle, it’s a bad sign.
I always watch for this when I pick up bottles in stores or from storage. If the liquid is moving or fizzing on its own, I leave it alone.
Visible rust or corrosion on the cap shows the drink was stored badly
According to the Safety Issues in Beverage Production, if there’s rust or a greenish film around the cap, don’t open the soda bottle. Rust, corrosion, or any kind of crust around the lid usually means the drink was kept somewhere damp or warm. That kind of storage can damage the seal and let air in. It also raises the risk of bacteria getting inside.
When I see anything like that on the cap, I throw the drink out without opening it.
Sticky residue around the lid could mean leakage or spoilage
If the bottle feels sticky around the cap, it may have leaked or started to ferment.
Sticky lids are something I’ve come across more than once. Sometimes it’s dried soda that leaked out. Other times it’s a sign that pressure pushed some of the drink up through the cap.
Now, I always check the cap and neck of the bottle. If it feels sticky or there’s residue, I don’t drink it.
Unusual pressure when opening means something is off inside the drink
If there’s no pressure at all or too much when opening, the soda may have gone bad.
Normally, when I open a fresh soda, I expect a quick, light hiss. But one time, I opened a bottle and nothing happened. No sound.
Another time, the opposite happened. I opened a soda, and it fizzed over like a volcano. It hadn’t been shaken. That kind of reaction usually means the drink has built up too much gas, possibly from spoilage or fermentation.
That’s all.
