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Keto soft drinks – Are diet or zero fizzy drinks ok?

Normal soft drinks like Coca-cola and Pepsi are full of sugar and should be completely avoided on keto. However, most brands do offer Diet or Zero versions that replace the sugar with a suitable sweetener. But are they keto-friendly?

Short answer: Yes, almost all diet versions of your favourite soft drink are fine.

Read on for a more in-depth understanding of why diet soft drinks are OK on keto.

Sweeteners in soft drinks

erythritol sugar free sweetener for tea

In order for a diet version of a soft drink to have a similar taste to the normal version, brands replace the sugar with sweeteners. The most common are Aspartame and Sucralose.

I’m sure you’ve heard the news stories that these sweeteners may have long term health impacts. However, there is no clear evidence that these are actually bad for you. Studies have been completed that reported side effects in some people. Although, further studies have been unable to replicate the findings or they require such high doses that would never be found in regular food or drink.

What makes these types of sweeteners great in diet drinks is that they don’t tend to cause an insulin response. Meaning that your blood sugar doesn’t spike, which can commonly result in you craving sugary food.

That being said, some people do report sugary cravings after ingesting diet soft drinks as well as it impeding their weight loss. A smaller subset have found that cutting sweeteners out altogether can help to break long weight loss plateaus. If you’re in a similar boat then why not try omitting sweeteners for a bit and see how you feel.

On a personal note, I still drink diet soft drinks on keto and have not had any problems over the past couple of years. On average I probably have a 330ml can a day and not seen any adverse effects. I’ve even take a blood ketone reading before and after consumption and there has been no noticeable difference.

Side note – if you want to find out more about sweeteners, then check out our article on sweeteners for tea.

What to look out for

Not all diet, low calorie and zero versions are the same. Some versions still contain some sugar or other carb-containing ingredient. Always check the nutrition label before purchase.

As an example, here are some products to avoid (unless you can fit them in your macros):

  • Fanta Orange Fruit Twist Zero – 0.5g carbs per 100ml 330ml can contains 1.7g of carbs
  • Fanta Zero Grape – 0.7g per 100ml 330ml can contains 2.3g of carbs
  • Tango Sugar Free Tropical – 0.5g carbs per 100ml 330ml can contains 1.7g of carbs
  • Diet Cloudy Lemonade – 0.6g carbs per 250ml (store-branded versions)

As you can see it’s mainly the diet versions of soft drinks made from fruit. This is because the fruit part still contains naturally-occurring sugars.


Everyone has their own favourite soft drink and almost all have a zero or diet version. Some of the most popular are listed below.


  • Diet (Amazon)
    • Exotic Mango
    • Caffeine Free
    • Twisted Strawberry
    • Sublime Lime
    • Feisty Cherry
  • Zero (Amazon)






  • Lemonade Slimline
  • Ginger Ale Slimline
  • Bitter Lemon Slimline – 0.1g per 100ml



All versions contain less than 0.5g of carbs per 100ml.

  • Zero
  • No Added Sugar
  • Watermelon, Strawberry & Peach No Added Sugar

Dr Pepper Zero

Old Jamaica Diet Ginger Beer

Store brand diet versions

Most UK supermarkets stock their own brand versions of popular soft drinks. Almost all are keto-friendly but some still contain trace carbohydrates (<0.5g per 100ml). Be sure to stay under your daily carb limit (average 20g per day).

  • Lemonade
  • Coke
  • Lemon & Lime
  • Cream Soda
  • Iron Brew
  • Dandelion & Burdock
  • Ginger Ale
  • Ginger Beer
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