For a quick top-up shop, choose the exact variety by its sugar declaration, then compare caffeine for the whole can—not just the can size or a sugar-free claim. Red Bull states that a 250ml Sugarfree can contains 80mg caffeine; Monster Energy lists 150mg in a 500ml Monster Ultra can. The smaller format offers a smaller stated single-can dose in these examples, but check the label of the particular variant you buy.
If sugars are your main concern, check the exact variety rather than relying on its brand name. Red Bull identifies Sugarfree as containing no sugars and says it uses sucralose and acesulfame K, which also matters if you avoid particular sweeteners.
Can size changes how much you consume in one go. Red Bull states 80mg caffeine per 250ml Sugarfree can, while Monster Energy lists 150mg per 500ml Monster Ultra can; confirm the figure on the variant in hand.
A no-sugar claim does not remove caffeine warnings. If you are buying for someone under 16, note that Newcastle City Council says England’s ban on sales of high-caffeine energy drinks to under-16s is scheduled to start in April 2027; retailers may also apply voluntary age policies.
For a top-up purchase, check the named variety and its ingredients first, then the caffeine amount for the quantity you intend to drink.
| Priority | What to check | Your needs |
|---|---|---|
| Sugars and sweeteners | Read the exact variety name, sugar declaration and ingredients list. Red Bull says Sugarfree uses sucralose and acesulfame K. | I want to avoid sugars, but I also want to know which sweeteners are in the can. |
| Caffeine per can | Compare the stated caffeine amount with the can volume. Red Bull gives 80mg per 250ml Sugarfree can; Monster Energy gives 150mg per 500ml Monster Ultra can. | A smaller single-can caffeine amount matters to me more than getting a larger drink. |
| Pack format | Check the number and size of cans, and decide how much of one can you plan to drink. Confirm caffeine on the precise variant’s label. | I’m topping up supplies and want a pack size that fits how I will use the cans. |
| Warnings | Read the high-caffeine warning and caffeine declaration. The UK Department of Health and Social Care states that drinks above 150mg caffeine per litre, other than tea or coffee, require a warning and a value in mg per 100ml. | I need to check who the drink is for and account for caffeine from other sources. |
Monster Energy lists 0g sugar and 150mg caffeine for its 500ml Monster Ultra; Red Bull states 80mg caffeine for a 250ml Sugarfree can. Sugar and caffeine answer different questions.
Compare caffeine for the whole can and consider other sources of caffeine you expect to have that day.
A range name does not establish the sugar content of every can. Relentless named a Zero Sugar Raspberry variety in a 2024 promotion, while Lucozade’s description of its Alert range does not establish that every Alert drink has no sugar.
Read the exact can’s sugar declaration, ingredients and caffeine information before choosing it.
A drink without sugars can still contain sweeteners: Red Bull identifies sucralose and acesulfame K in Sugarfree.
If particular ingredients matter to you, check the ingredients list as well as the sugar declaration.
Red Bull identifies Sugarfree and Zero as no-sugar varieties with different sweetener formulations and tastes.
Monster Energy describes its 500ml Monster Ultra as a zero-sugar drink.
A Relentless promotion in 2024 named a 500ml Zero Sugar Raspberry variety.
Lucozade describes Alert as a high-caffeine drinks range.
Tesco’s grocery category has listed sugar-free energy drinks, including named Red Bull and Monster varieties.
These multipacks cover 250ml Red Bull Sugarfree and Zero cans and a larger 500ml Monster Ultra White format. Check the exact can label when comparing sugars, sweeteners and caffeine.
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A four-pack of smaller cans for shoppers comparing caffeine per serving. Red Bull states that Sugarfree contains no sugars and has 80mg caffeine per 250ml can; it identifies sucralose and acesulfame K as sweeteners.
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Another four-pack of 250ml cans to consider when avoiding sugars. Red Bull identifies Zero as a no-sugar variety distinct from Sugarfree; check Zero’s own ingredients and caffeine declaration rather than assuming the formulations are identical.
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This 12-pack offers a larger can format than the 250ml options. Check the sugar declaration and caffeine amount on the exact Ultra White can before choosing a full-can serving; do not assume the figure for another Monster Ultra product applies to this variant.
No. Red Bull states that a 250ml Sugarfree can has 80mg caffeine, while Monster Energy lists 150mg in a 500ml Monster Ultra can with 0g sugar. Check the caffeine amount for the exact can you intend to drink.
Read the exact variety’s sugar declaration and ingredients list, then check caffeine separately. Red Bull says Sugarfree contains no sugars but uses sucralose and acesulfame K, so avoiding sugars does not necessarily mean avoiding sweeteners.
No. It tells you about sugars, not whether the drink is suitable during pregnancy. Read the caffeine amount and any high-caffeine warning, and account for caffeine from other drinks and foods; seek individual medical advice where needed.
The UK Department of Health and Social Care states that drinks other than tea or coffee containing more than 150mg caffeine per litre require a warning and must declare caffeine in mg per 100ml. Read the can size too, so you can assess the amount in the whole can.
Newcastle City Council says England’s ban on sales of high-caffeine energy drinks to under-16s is scheduled to come into force in April 2027, covering shops, vending machines and online sales. Before then, a retailer may apply its own voluntary age policy; do not assume the same rules apply outside England.