Adults wanting one sugar-free journey drink
Compare the size of the can and its total caffeine, not just the words on the front of the pack.
Who is this choice for?
Travellers keeping track of caffeine
If you also drink coffee, tea or cola, consider the caffeine in your train drink alongside everything else you consume that day.
People checking age or pregnancy warnings
Read the warning on the exact drink. If buying for someone under 16, also check the retailer’s age policy; during pregnancy, take account of caffeine from all sources.
What should you check before buying?
Start with the sugar declaration and caffeine for the whole container, then decide whether its size and any after-opening instructions work for your journey.
| Priority | What to check | Your needs |
|---|---|---|
| Sugar and caffeine | Read both the sugar declaration and caffeine amount. Red Bull lists 80 mg caffeine per 250 ml Sugarfree can; Monster Energy UK lists 150 mg per 500 ml Ultra can. | I want to avoid sugar without mistaking a zero-sugar label for a caffeine-free drink. |
| Whole-day caffeine | Compare caffeine for the complete can, not just per 100 ml. Include other caffeinated drinks and products you expect to have that day. | A train drink needs to fit with the coffee, tea or cola I may also have. |
| Size and storage | Check whether you want a 250 ml or 500 ml can. For the 900 ml Lucozade Energy Zero Sugar Orange bottle listed by Sainsbury’s, check its instruction to refrigerate after opening. | I would rather carry a container I can use on the journey than open a larger bottle I cannot store as instructed. |
| Warnings and age policy | Read the exact can’s caffeine warning and check the retailer’s age policy. Sainsbury’s says it does not sell high-caffeine energy drinks to under-16s. | If I am buying for someone else, I need to check the warning and whether the retailer will sell them the drink. |
What is easy to overlook?
-
Reading “zero sugar” as “no caffeine”
Zero-sugar drinks can still contain caffeine: Red Bull lists 80 mg per Sugarfree can, while Monster Energy UK lists 150 mg per Ultra can.
Check caffeine for the whole container and include any other caffeinated products you plan to have that day.
-
Choosing a large can by volume alone
Monster’s 500 ml Ultra can has more caffeine per can than the 250 ml Red Bull Sugarfree example, according to their respective UK product pages.
Choose the container size alongside its stated caffeine amount, rather than treating volume as the only difference.
-
Treating a large zero-sugar bottle as a single serving
Sainsbury’s lists Lucozade Energy Zero Sugar Orange in a 900 ml bottle whose ingredients include caffeine. Its after-opening instruction calls for refrigeration.
Check the bottle size, ingredients and storage instructions before packing it for a train journey.
-
Confusing a retailer age policy with UK-wide law
Sainsbury’s says it does not sell high-caffeine energy drinks to under-16s. Separately, the Department of Health & Social Care described an intended ban on sales to children in its July 2026 consultation; an intention is not an enacted UK-wide rule.
Check the retailer’s policy and the rules applicable where you are buying.
Brand and product-line references
Red Bull
Sugarfree is a compact-can option for an adult comparing sugar status and caffeine per drink.
- Red Bull states that each 250 ml Sugarfree can contains 80 mg caffeine and no sugar.
- It is not a caffeine-free option.
Monster
Monster Energy UK describes Ultra as a zero-sugar drink in a 500 ml can.
- Its UK product page lists 150 mg caffeine per can.
- That is more caffeine per complete can than the 250 ml Red Bull Sugarfree example.
Lucozade
Sainsbury’s lists Energy Zero Sugar Orange as a bottled zero-sugar option whose ingredients include caffeine.
- The researched bottle contains 900 ml for those considering a larger format.
- Sainsbury’s instructs buyers to refrigerate it after opening.
Relentless
Check the specific Relentless product rather than assuming every flavour is sugar-free.
- The official White Citrus description identifies caffeine in the drink.
- That same description says White Citrus contains sugar and sweetener, so it does not meet a zero-sugar requirement.
Joybuy drinks for a train journey
These multipacks offer 250 ml, 355 ml and 500 ml cans to consider for a journey. Check the caffeine statement on the exact can, particularly when choosing the larger Monster pack.
No image available
Red Bull Sugarfree Energy Drink, 250 ml × 4
The 250 ml can is a compact size for one journey; this listing is a four-pack. Red Bull states that Sugarfree contains 80 mg caffeine per can and no sugar. Account for other caffeine you have that day.
No image available
CELSIUS Kiwi Guava, 355 ml × 12
The 355 ml cans come in a 12-pack rather than as a single-can purchase. Check the sugar and caffeine figures on the exact can before choosing one for your journey.
No image available
Monster Energy Ultra Zero Sugar, 500 ml × 4
This four-pack provides larger, 500 ml zero-sugar cans. Check the caffeine amount on the exact can before choosing it alongside other caffeinated drinks.
Frequently asked questions
Does zero sugar mean caffeine-free?
No. Red Bull lists 80 mg caffeine in a 250 ml Sugarfree can, and Monster Energy UK lists 150 mg in a 500 ml Ultra can. Sainsbury’s also lists caffeine among the ingredients of Lucozade Energy Zero Sugar Orange.
Which container size works for one train journey?
Choose a size you are comfortable carrying and drinking, while checking its whole-container caffeine amount. The Red Bull Sugarfree example is a 250 ml can; Monster Ultra is 500 ml. Sainsbury’s 900 ml Lucozade Energy Zero Sugar Orange bottle requires refrigeration after opening.
Can someone under 16 buy a high-caffeine energy drink?
Check the retailer’s policy and the rules where the purchase takes place. Sainsbury’s says it does not sell high-caffeine energy drinks to under-16s; that retailer policy alone does not establish a UK-wide legal rule.
What should a pregnant traveller check?
Read the drink’s caffeine warning and consider caffeine from all sources, not just the journey drink. For advice about an individual pregnancy, speak to a healthcare professional rather than treating a product label as personalised guidance.