During-effort fuel · gel · reviewed 28 Aug 2026
SiS GO Isotonic Energy Gel 18
SiS's original isotonic gel, built on maltodextrin alone with no fructose blend at all, works without chasing it with water by design, at $0.098 a gram of carbohydrate against Beta Fuel's $0.063 and Maurten's $0.150.
Score breakdown
The overall score is the average of what's below, each measured against every other gel we've reviewed.
18
Weak
Based on 4 of 5 measures ?A dimension a product doesn't declare is left out of its average rather than counted against it -- so this score reflects fewer measures than a product with a full panel.
Carb density ?How much fuel one sachet carries. 90 g is the ceiling here, matching the top of the range cited for multi-transportable-carb intake.24
Sodium ?Sodium carried by the gel itself, on a scale topping out at 1000 mg — the upper end of what's typically lost to sweat in an hour.0
Value (cost/gram) ?Price of one gram of carbohydrate. Not physiological -- a market-based scale from $0.15/g (0) to $0.02/g (100).28
Gut comfort ?A proxy, not a taste or tolerance test: shorter ingredient lists score higher, from 15 ingredients (0) to 1 (100). Nobody has actually run these through anyone's gut for this score.21
Cost per gram of carbohydrate
$0.113/g
Glucose : fructose · not disclosed
n/d
Comparison
6 of 22 gels heldPrices per single sachet at the cheapest box size we track. Best in green, worst in red, across the gels shown.
| Measure | Science in Sport SiS GO Isotonic Energy Gel | Maurten Maurten Gel 100 | Science in Sport SiS Beta Fuel Gel | Precision Fuel & Hydration Precision Fuel PF 30 Gel | NEVERSECOND NEVERSECOND C30 Gel | GU Energy Labs GU Original Energy Gel |
|---|---|---|---|---|---|---|
| CarbohydrateHow much fuel one sachet carries. | 22 g | 25 g | 40 g | 30 g | 30 g | 22 g |
| Glucose : fructoseGoverns how fast you absorb it. More fructose, higher ceiling. | n/d | 1 : 0.8 | 1 : 0.77 | 1 : 0.5 | 1 : 0.5 | ~ 1 : 0.47 |
| SodiumAgainst 400 to 1000 mg an hour typically lost in sweat. | 4 mg | 20 mg | 30 mg | not declared | 200 mg | 60 mg |
| ProvenanceWhether that ratio is read off the panel, computed from it, or inferred. | Not disclosed | Stated | Derived | Stated | Stated | Estimated |
| Price per sachetWhat one costs. Not comparable across sachet sizes. | $2.49 | $3.75 | $2.50 | $3.12 | $3.50 | $2.00 |
| Cost per gramThe only price that compares across sachet sizes. | $0.113 | $0.150 | $0.063 | $0.104 | $0.117 | $0.091 |
| Sachets for 90 g/hrHow many you open an hour to hold a 90 g/hr target. | 4.1 | 3.6 | 2.3 | 3.0 | 3.0 | 4.1 |
Verdict
what it does · what it costsWhat it does well
- True isotonic osmolality means it can genuinely be taken without water, unlike SiS's own thicker 40 g Beta Fuel Gel.
- Single carbohydrate source, maltodextrin only, so there's no glucose:fructose blend to manage or tolerate.
- A third cheaper per gram than Maurten Gel 100 at $0.150 a gram.
What it costs you
- 22 g of carbohydrate is the smallest sachet SiS sells, meaning about 4 sachets an hour to hold 90 g/hr.
- No dual-source blend at all, so there's no ratio science here the way there is with Beta Fuel or Maurten.
- 4 mg of sodium is effectively nothing; you'll need a separate electrolyte source.
Where to buy
Prices and links as last checked.
Who this is for
the numbers, appliedThe field tells you what it is. This is who should act on it.
Worth the money if
- You want a gel that genuinely doesn't need water chased with it.
- You'd rather have a plain single-source maltodextrin gel than manage a blended ratio.
Look elsewhere if
- You're targeting 90 g/hr or more and don't want to carry four-plus sachets an hour.
- You want the dual-source ratio that Beta Fuel or Maurten are built around.