Choose a sugar-free energy drink before a workout if you want a caffeinated drink, not a substitute for a carbohydrate-containing snack. Red Bull UK states that a 250 ml Sugarfree can contains 80 mg caffeine; Monster Energy UK lists 150–160 mg for the specific 500 ml Ultra variants discussed here. Compare the amount in the whole can with your other caffeine intake, and check the exact product label.
If you also drink coffee or tea, compare caffeine per complete can rather than choosing by can size alone. Red Bull UK states 80 mg per 250 ml Sugarfree can; Monster Energy UK states 150 mg per 500 ml Ultra White can.
Check whether the exact can says “no added sugars”, “sugar-free” or “zero sugar”, then read its nutrition panel and ingredients. A drink without sugar does not take the place of food if carbohydrate is part of your pre-workout plan.
Sugar-free does not mean caffeine-free. Pregnancy, caffeine sensitivity and purchases for children call for particular attention to the can’s warnings, caffeine amount and applicable guidance.
Start with the sugar declaration, compare caffeine for the whole can, then decide separately whether you want food before training.
| Priority | What to check | Your needs |
|---|---|---|
| Sugar claim | Read the exact claim, ingredients and nutrition panel for the chosen variant. The National Archives’ published conditions for a “no added sugars” claim exclude added sugars and other foods used for sweetening; do not treat that wording and “zero sugar” as interchangeable. | I want a drink without sugar, and I need to know what the particular can contains rather than relying on a search category. |
| Caffeine per can | Check caffeine for the complete can and the exact flavour. Red Bull UK states 80 mg per 250 ml Sugarfree can; Monster Energy UK states 150 mg per 500 ml Ultra White can and 160 mg per 500 ml Ultra Fantasy Ruby Red can. Monster notes that its figures may vary by region. | A smaller single-can caffeine amount would be easier for me to account for alongside other caffeinated drinks or supplements. |
| Food before training | Keep the drink decision separate from the food decision. Check the drink’s sugar and carbohydrate declaration if you are counting on it to supply carbohydrate. | If carbohydrate is part of my pre-workout plan, I need to choose food as well as, or instead of, a sugar-free drink. |
| Caffeine cautions | Add up caffeine from all sources and read the can’s warnings. The European Food Safety Authority’s 2015 opinion gives different caffeine-intake conclusions for healthy adults and pregnancy; those figures are not individual targets. | Before choosing a can, I want its caffeine amount to make sense alongside everything else I may consume that day. |
“No added sugars” has specific claim conditions, while a zero-sugar statement describes the particular product. A drink without sugar may still contain sweeteners.
Read the exact wording, ingredients and nutrition panel on the variant you intend to buy.
Red Bull UK states 80 mg caffeine per 250 ml Sugarfree can. Monster Energy UK states 150 mg per 500 ml Ultra White can and 160 mg per 500 ml Ultra Fantasy Ruby Red can.
Use the complete-can figure for the exact variant, then account for other caffeine you consume that day.
A zero-sugar drink does not supply sugar as a source of carbohydrate, even if it contains caffeine.
If your pre-workout plan includes carbohydrate, make a separate food choice rather than assuming the drink covers it.
Sugar content does not change a drink’s caffeine amount. A Department of Health and Social Care consultation outcome updated on 16 July 2026 said the government intended to introduce an under-16 sales restriction for high-caffeine energy drinks in England through secondary legislation; that statement does not establish an active UK-wide ban.
Read caffeine warnings and check the current law and retailer requirements when purchasing for a child. For pregnancy, account for caffeine from all sources and follow applicable clinical advice.
Red Bull Sugarfree is a 250 ml option for comparing a smaller single-can caffeine amount with the 500 ml Ultra products discussed here.
The specific 500 ml Ultra variants here offer larger complete-can caffeine amounts than Red Bull Sugarfree 250 ml, according to the manufacturers’ figures.
Lucozade Zero is a zero-sugar soft-drink range to consider when a particular energy-drink caffeine amount is not the reason for buying.
Check the variant rather than assuming every Relentless drink meets a no-sugar requirement.
These Joybuy multipacks offer sugar-free or zero-sugar energy-drink variants. Compare the individual can and its caffeine label, not just the pack format.
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For comparing a smaller individual can with the 500 ml options before a workout.
The pack contains 24 cans of 250 ml. Red Bull UK states that Sugarfree contains 80 mg caffeine per 250 ml can. Account for any other caffeine you consume.
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For shoppers considering the Green Zero Sugar variant in a multipack.
The pack contains 12 cans. Check caffeine per individual can on the exact product label before including it in your daily total.
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For shoppers comparing a zero-sugar Ultra variant in a 500 ml can format.
The stated bundle format is 6x4x500 ml. Check caffeine on the individual can before planning your intake; do not assume every Ultra variant has the same amount.
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For shoppers who want the Zero variant in a 250 ml can format.
The pack contains eight cans. Check caffeine on the Red Bull Zero can rather than applying the figure for Red Bull Sugarfree, which is a different variant.
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For shoppers considering a zero-sugar Ultra White multipack with 500 ml cans.
Monster Energy UK states 150 mg caffeine per 500 ml Ultra White can, while this Joybuy listing states 160 mg per can. Check the exact can label before using either figure to plan your intake.
No. The claim conditions published by The National Archives say that a product making a “no added sugars” claim must not contain added mono- or disaccharides or another food used for sweetening. Check the exact can’s claim, nutrition panel and ingredients rather than treating the two phrases as identical.
Red Bull UK states that Sugarfree contains 80 mg caffeine per 250 ml can. Monster Energy UK states 150 mg per 500 ml Ultra White can and 160 mg per 500 ml Ultra Fantasy Ruby Red can; its figures may vary by region. Check the can you are buying, particularly where a listing gives a different figure.
Not if you are relying on that snack to provide sugar as carbohydrate. Decide whether you want a caffeinated drink and whether you also want food before training; the drink’s caffeine content does not answer the food question.
Count caffeine from all sources, not just the energy drink. The European Food Safety Authority’s 2015 opinion states that up to 200 mg per day from all sources does not raise safety concerns for the fetus; the Royal College of Midwives’ 2024 summary gives the same daily amount for NHS and RCOG guidance. This is not a suggested amount to consume, and individual advice may differ.
The Department of Health and Social Care’s consultation outcome, updated 16 July 2026, stated an intention to introduce an under-16 sales ban for high-caffeine energy drinks in England through secondary legislation; it did not establish an active UK-wide ban. Check the current law and the retailer’s requirements at the time of purchase.