Runners who have already eaten
If you want caffeine without sugar, compare the caffeine in the whole serving. A zero-sugar label does not tell you how much caffeine the can contains.
Who is making this choice?
Runners who have missed breakfast
If carbohydrate is what you need before the run, consider food or a carbohydrate drink instead of relying on a zero-sugar energy drink. The UK Sports Institute identifies a carbohydrate drink as an option when there has been no time for breakfast.
Younger or caffeine-sensitive shoppers
Check the warning on the exact product before considering it for a run. Relentless, for example, says its White Citrus drink is not recommended for children or people sensitive to caffeine.
What should you check before buying?
Decide whether you need carbohydrate or are considering caffeine, then check the full serving and how it fits your usual pre-run routine.
Zero-sugar energy drink
Consider it when: You have eaten and want a caffeinated drink without sugar.
Trade-off: It is not a substitute for missed carbohydrate fuel, and caffeine varies substantially between cans.
Sugar-containing energy drink
Consider it when: You specifically want a drink containing carbohydrate and have checked its caffeine and sugar information.
Trade-off: Its sugar content does not establish that it is preferable to food or a carbohydrate drink for your run.
Food and water, or a carbohydrate drink
Consider it when: Pre-run carbohydrate, rather than caffeine, is the decision. The UK Sports Institute suggests a carbohydrate drink as an option if breakfast was missed.
Trade-off: Food and drink timing depends on what you tolerate; a zero-sugar sports drink does not serve the same carbohydrate purpose.
| Priority | What to check | Your needs |
|---|---|---|
| Carbohydrate | Read the carbohydrate amount for the serving, not just the product name. The UK Sports Institute says a carbohydrate drink can be useful after a missed breakfast but is probably unnecessary after a carbohydrate-based breakfast. | I have not eaten before the run and want to know whether this drink provides carbohydrate, rather than caffeine alone. |
| Caffeine | Compare caffeine per whole can and account for other sources that day. Red Bull United Kingdom states 80 mg per 250 ml Sugarfree can; Monster Energy United Kingdom states 160 mg per 500 ml Absolutely Zero can. | A zero-sugar label is not enough for me: I want to know the caffeine amount in the portion I would actually drink. |
| Pre-run routine | Check the serving size, product warnings and whether you have tried that portion and timing during training. UK Sports Institute guidance notes that food timing and tolerance vary between runners. | I would rather use a familiar food or drink than try a new caffeinated, carbonated can immediately before an event. |
Common buying mistakes
-
Assuming zero sugar means little caffeine
Red Bull United Kingdom states 80 mg caffeine in a 250 ml Sugarfree can, while Monster Energy United Kingdom states 150 mg in a 500 ml Ultra can and 160 mg in a 500 ml Absolutely Zero can.
Read the caffeine amount for the exact whole can and consider caffeine from coffee, tea and other drinks too.
-
Using a diet drink in place of missed food
A zero-sugar choice does not serve the same carbohydrate purpose as the food or carbohydrate drink discussed in UK Sports Institute guidance for runners who missed breakfast.
If carbohydrate is the reason you are choosing a pre-run drink, check its carbohydrate content or consider food you already tolerate.
-
Treating every ‘sport’ or ‘energy’ label alike
Lucozade describes Sport Zero as a zero-sugar drink with electrolytes. Its name does not mean it provides carbohydrate fuel.
Check sugar, carbohydrate, caffeine and serving size on the individual product rather than choosing by range name.
-
Overlooking caffeine warnings
Relentless says its White Citrus drink is not recommended for children, people sensitive to caffeine, pregnant women or women who are nursing.
Read the warning on the exact pack; do not treat an energy drink as routine running fuel for someone covered by it.
Relevant brands and retailer references
Red Bull
Red Bull United Kingdom lists Sugarfree in a 250 ml can.
- The brand states 80 mg caffeine per 250 ml Sugarfree can.
- Sugarfree is a caffeine-without-sugar choice, not a replacement for carbohydrate food after a missed meal.
Monster
Monster Energy United Kingdom lists zero-sugar Ultra and Absolutely Zero in 500 ml cans.
- The brand states 150 mg caffeine and 0 g sugar for a 500 ml Ultra can, and 160 mg caffeine and zero sugar for a 500 ml Absolutely Zero can.
- Check the exact variant and whole-can caffeine amount rather than applying one range figure to every pack.
Lucozade
Lucozade distinguishes its Zero drinks from Sport Zero, which it describes as a zero-sugar fitness drink with electrolytes for low-intensity exercise.
- The range names give shoppers different formulations to check against their intended use.
- Do not choose a zero-sugar variant when the purpose is to obtain carbohydrate.
Relentless
Relentless lists sucrose and caffeine in its White Citrus drink.
- White Citrus is an example to inspect if considering a drink containing both sugar and caffeine.
- Its product warning says it is not recommended for children, people sensitive to caffeine, pregnant women or women who are nursing.
Tesco
Tesco Groceries lists regular and sugar-free energy-drink variants in its online category.
- The category includes Red Bull Sugar Free, Monster Ultra and Relentless products for comparing individual labels.
- A category listing does not establish that a particular variant suits pre-run fuelling or caffeine preferences.
Joybuy drinks to compare
These energy drinks include zero-sugar-labelled options and a Lucozade Energy bottle. Compare each exact pack against whether you want carbohydrate, caffeine, or neither before a 5K.
No image available
CELSIUS Watermelon Strawberry, 12 × 355 ml
For a pre-run drink choice, check the sugar and caffeine information for each 355 ml can and try the portion during training. Do not use a zero-sugar drink in place of missed carbohydrate food.
No image available
Red Bull Sugarfree, 4 × 250 ml
Consider this sugar-free option if you have eaten and want caffeine rather than carbohydrate fuel. Red Bull United Kingdom states 80 mg caffeine per 250 ml Sugarfree can; include other caffeine sources when judging the whole serving.
No image available
Applied Nutrition Body Fuel Orange Flavour, 12 × 330 ml
If you are considering this drink before a 5K, check carbohydrate and caffeine for the whole 330 ml can. Try the exact drink during training rather than relying on the Body Fuel name to establish its role.
No image available
Monster Energy Ultra Zero Sugar, 4 × 500 ml
This zero-sugar option is not a substitute for missed carbohydrate food. Check caffeine on the exact 500 ml pack before choosing it, and account for other caffeine you consume.
No image available
Lucozade Energy Orange, 8 × 380 ml
If you missed a pre-run meal and are considering a drink for carbohydrate, check the amount per 380 ml bottle. Also check the bottle's caffeine information and try the portion and timing during training.
Questions about drinks before a 5K
Will a zero-sugar energy drink fuel my 5K?
Not if you mean replacing missed carbohydrate food. UK Sports Institute guidance suggests a carbohydrate drink as an option when breakfast was missed, but says a sports drink is probably unnecessary after a carbohydrate-based breakfast. Check the exact drink's carbohydrate content rather than treating caffeine as fuel.
How should I compare caffeine between cans?
Compare the amount in the whole can and include caffeine from other sources. Red Bull United Kingdom states 80 mg per 250 ml Sugarfree can; Monster Energy United Kingdom states 150 mg per 500 ml Ultra can and 160 mg per 500 ml Absolutely Zero can. Those figures describe the named products, not every variant or pack.
Is a zero-sugar sports drink the same as a carbohydrate drink?
No. Lucozade describes Sport Zero as a zero-sugar drink with electrolytes for low-intensity exercise; its sport positioning does not make it a carbohydrate-fuelling choice. Check sugar and carbohydrate separately from caffeine on whichever drink you are considering.
Should I try a new energy drink immediately before a 5K event?
Try the exact drink, portion and timing during ordinary training instead. UK Sports Institute guidance notes that runners vary in what and when they tolerate food before running, so an unfamiliar pre-run routine adds an avoidable uncertainty.