Drink Mix Builder

A DIY sports drink is a homemade electrolyte and carbohydrate solution mixed from bulk ingredients - typically maltodextrin, fructose, and sodium citrate - rather than a pre-packaged commercial product. Endurance athletes formulate their own drinks to control exact carbohydrate ratios, sodium content, sweetness, and osmolality, often at a fraction of the cost of branded products.

This builder lets you mix ingredients in real time and see the precise nutritional output: total carbohydrates, sodium, glucose-to-fructose ratio, osmolality in mOsm/L, and carbohydrate concentration as a percentage. You can also load formulations back-calculated from nine commercial sports drinks to understand what those products actually contain.

Consult a sports dietitian for personalised race nutrition advice. Osmolality values are estimates based on ingredient molecular weights.

1. Load a brand preset or start blank The brand chips load back-calculated formulations from commercial products. Use them as a reference starting point.
2. Adjust carb sources Mix maltodextrin (glucose), fructose, table sugar (50/50 glucose + fructose), and honey. The donut chart updates live with your glucose:fructose split.
3. Add sodium Sodium citrate gives milder flavour; table salt gives more sodium per gram. Target 400-700mg per hour for most race conditions - per bottle if you are drinking roughly one an hour. Guidelines cluster at 345-700mg per litre, and note they disagree: Rowlands et al. (2022) recommend the lower end for holding plasma volume, while the ISSN's ultra-marathon stand argues for above 575mg/L to manage hyponatremia risk over many hours.
4. Choose your fluid volume Select 500ml, 750ml, or 1000ml. Osmolality halves when you double the water - adjust to keep the needle in the green.
5. Set consumption rate (optional) Select bottles per hour to reveal SGLT1 and GLUT5 transporter utilisation bars. These show whether your hourly intake exceeds absorptive capacity.
6. Refine and save The URL updates automatically. Bookmark your formula to access it again without re-entering values.

Osmolality is calculated from the molar concentration of dissolved particles: mOsm/L = (grams / molecular_weight) x particles x 1000 / volume_L. Maltodextrin (1 particle per molecule) contributes very few mOsm despite carrying many carbohydrate calories. Its molecular weight depends on the dextrose equivalent of your product: because DE is reducing sugars as a percentage of dextrose and each chain has one reducing end, the average MW is 18016/DE - about 1000 g/mol at DE18, but 1800 at DE10. That doubles the osmolality of the same grams, which is why the builder lets you set DE. Fructose and glucose (MW 180, 1 particle) contribute moderately. NaCl (MW 58.4, 2 particles from full dissociation) has an outsized osmolality contribution relative to its mass - 1g of NaCl adds 68 mOsm/L in 500ml. Sodium citrate splits into four particles (3 Na+ plus citrate3-) but is far heavier per molecule - MW 258 anhydrous, 294 as the dihydrate - so per gram it is less than half as osmotically potent as NaCl, not more. Per milligram of sodium delivered it is the cheaper option, about 58 mOsm per 1000mg of sodium against 87 for NaCl, and that ratio is the same for either hydrate. This tool sums moles x particles over the water you add, which approximates osmolality (mOsm/kg of water) - the basis the tonicity bands above are defined on. Treat it as a calculated estimate rather than an osmometer reading: it tracks measured values closely at ordinary strengths but reads low for very concentrated mixes, and the average molecular weight of a real maltodextrin varies by roughly 15% between batches. We report the bands from Rowlands et al. (2022); other references, including EFSA, draw the isotonic window slightly differently at 270-330.

Dual-transporter carbohydrate absorption (Jeukendrup & Moseley, 2010) is the key principle behind modern sports nutrition. Glucose uses SGLT1 (sodium-dependent glucose transporter 1), saturating at ~60g/hr. Fructose uses GLUT5, saturating at ~30g/hr. They are independent - a 2:1 mix allows simultaneous saturation of both pathways for ~90g/hr total absorption. This is why products like Maurten 160, SiS Beta Fuel, and Tailwind all contain both glucose sources and fructose.

Concentration vs osmolality. These two metrics diverge dramatically with maltodextrin. A 9% maltodextrin solution is strongly hypotonic (about 90 mOsm/L) because the large MW means few particles per gram. A 9% glucose solution is hypertonic (about 500 mOsm/L) - the same carbohydrate content, more than five times the osmotic load. This is why concentration alone is insufficient to predict gut tolerance - osmolality is the mechanistically relevant measure, and it is why commercial high-carb mixes can run at 15% and above without being unusable. It also tells you which slider to move: free fructose typically contributes 60-75% of the osmoles in a 1:0.8 mix - 72% of Beta Fuel's 556 mOsm/L comes from its 36g of fructose alone - so if a mix reads hypertonic, shifting grams from fructose to maltodextrin drops osmolality far faster than adding water.

Honey contains approximately 30% glucose and 38% fructose (of total honey weight), with the remainder being water, trace sugars, and non-sugar compounds - total carbohydrate around 82g per 100g (USDA FoodData Central). The builder models honey as 36% glucose and 47% fructose by weight, apportioning the maltose and minor sugars across the two so the 83% carbohydrate total is preserved. That makes honey a moderately fructose-dominant carbohydrate source.

Jeukendrup AE, Moseley L. (2010). Multiple transportable carbohydrates enhance gastric emptying and fluid delivery. Scand J Med Sci Sports. 20 Suppl 1:55-60. Thomas DT et al. (2016). Position of the Academy of Nutrition and Dietetics on nutrition and athletic performance. J Acad Nutr Diet. 116(3):501-528.