Table 1.

Study characteristics.

Study	Experimental design	Subjects	Supplementation	Fluid replenishment time and dose	Exercise protocol	Results
Hogervorst et al. (1999)	Double-blind RCT with a crossover design	15 healthy male competitive cyclists or triathletes (23.3 ± 3.6 years)	1) Placebo water 2) Placebo- carbohydrates 68.8 g/L 3) carbohydrates combined with caffeine 150 mg/L 4) with caffeine 225 mg/L 5) with caffeine 320 mg/L. Each subject was tested at different times for 5 solutions.	With 8 mL fluid/kg body weigh ingestion before trial at warm-up session and 3 mL fluid/kg body weigh ingestion every 20 min during the trial.	An all-out 1 h time trial on a bicycle ergometer.	The Stroop Color-Word Test. Signal Detection Task. The Motor Choice Reaction Time Test and the visual Verbal Learning Test with Interference were measured.
Pomportes et al. (2019)	Single-blind RCT with a pseudo counter-balanced design	10 pentathlon athletes (6 males and 4 females, age 18.6 ± 2 years)	1) A 6% carbohydrate complex 2) A 200 milligrams (mg) caffeine added with orange sugarless syrup 3) A 3.4 grams (g) guarana complex 4) A placebo.	Two before exercise and one during exercise.	The exercise involved a 40 min run on a treadmill at a steady speed and each athlete participates four times.	Simon tasks were measured.
Winnick et al. (2005)	Double-blind RCT	20 active men (N = 10,24.9 ± 2.08 years) and women (N = 10,22.9 ± 1.45 years), with experience competing in team sports.	1) A 6% CHO solution 2) A flavored placebo (PBO).	Subjects received 5 mL/kg of fluid before exercise and 3 mL/kg after exercise, in addition to 3 mL/kg over a 5 min span after the first and third quarters, and 8 mL/kg during a 20 min halftime. Consumption of carbohydrate was approximately 41 g h−1 in the CHO trial.	Four 15 min quarters of shuttle running with variable intensities ranging from walking (30%VO2max), to running (120%VO2max), to maximal sprinting, and 40 jumps at a target hanging at 80% of their maximum vertical jump height.	The Stroop Color and Word Test were measured.
Zhu et al. (2020)	A single-blind RCT with a cross-over design.	14 male soccer athletes (age, 24.3 ± 3.7 years)	1) Control (electrolyte solution without CHO) 2) CHO (4.2 g/100 mL CHO, 3 mL/kg in each trial), 3) CHO-M (brief MBI).	Participants were instructed to consume 3 mL/kg in each trial during the half-time break.	Soccer games.	The Stroop effect task (ST), Corsi-block-tapping test (CBT), and rapid visual information processing task (RVIPT)
Dupuy and Tremblay (2019)	RCT	85 recreationally active males (24.4 ± 4.6)	1) Water (control) 2) Glucose (60 g/L) 3) A commercial sports drink (CSD) 4) Diluted maple syrup 5) Concentrated maple water.	Subjects ingested 166 mL of the experimental solution, drinking a total of 1 L of the same solution throughout the experimentation.	Six 3 min bouts at 95% of their maximal aerobic power on a stationary bike, with 3 min of passive rest between efforts.	Plasma glucose concentration, peak power output, maximal oxygen consumption, cognitive task and cerebral oxygenation were measured. Cognitive performance was assessed by the computerized modified Stroop task.
Harper et al. (2017)	Randomised, crossover.	15 male University soccer players (age: 22 ± 2 years)	1) Water; WAT 2) Carbohydrate-electrolyte, 12% CHO, 60 g·500 mL−1 3) Placebo-electrolyte; PL)	Beverages were ingested towards the end of the warm-up (250 mL) and at HT (250 mL); both <15 min before each half commenced.	90 min of soccer-specific exercise (including self-paced 6 exercise at the end of each half).	Physical, technical and cognitive (memory, attention, decision making) performance were assessed.
Sun et al. (2020)	Double-blind RCT with a crossover design	16 male college soccer players (21 ± 1 years)	1) Carbohydrate-electrolyte-solution (CES,6% CHO in the form of sucrose) 2) Carbohydrate-electrolyte-protein-solution (CEPS,4% CHO in the form of sucrose plus 2% whey PRO) 3) Placebo (PLA).	Before warming up (5 mL/kg BM) and every 15 min thereafter (during resting period, 2 mL/kg BM).	In each trial, they completed 30 min of 70% VO2peak cycling, and one of two solutions (CES or CEPS) was consumed.	The Visual Search Test, the Stroop Test, and the Rapid Visual Information Processing Test were measured.
Pomportes et al. (2016)	A double blind, randomized, crossover research design	17 high-level squash and fencing athletes (7 females and 10 males, 19.1 ± 1 years)	1) 7% carbohydrate complex (CHO: fructose and maltodextrine, Isoxan Sport) 2) Placebo (Pl, 250 mL tap water added with orange sugarless syrup).	During each experimental session, subjects ingested 60 min (Ing1) and 30 min (Ing2) before exercise either 250 mL of a 7% carbohydrate complex or placebo.	6 sprints (5 s) with a passive recovery (25 s) followed by 15 min submaximal cycling.	Physiological parameters, perceived exertion, shooting performance and cognitive function were measured. Cognitive function included a simple reaction time (SRT) task at rest, a visual scanning task (VS) and a Go/No-go task (GNG) during a submaximal cycling exercise.
Wong et al. (2014)	Randomized crossover study design	9 healthy active males (n = 9) and 10 eumenorrheic females (n = 10), 23.1 ± 1.2 years for males, 22.6 ± 0.8 years for females.	1) Carbohydrate-electrolyte solution (CES, CHO 6.6%) 2) Lemon tea (LT) 3) Distilled water (DW)	The total intake volume of fluid during REC was equivalent to 150% of BM loss during the previous 60-min run. The fluid was consumed in 6 equal volumes at 30, 60, 90, 120, 150, and 180 min of the REC.	All participants completed a 60 min moderate endurance run at 60% VO2max on a motorized treadmill in a hot and humid environment (temperature: 29.2 ± 0.9°C; relative humidity: 71 ± 5%) of 3 times. Immediately after the run, the 4 h recovery (REC) period commenced.	Plasma volume (PV) changes, serum osmolality, plasma sodium, potassium concentrations, abdominal discomfort (AD), stomach fullness (SF), and the CogState battery were measured.
Pollow et al. (2016)	Double-blind RCT with a crossover design.	7 well-trained cyclists and triathletes (26.9 ± 3.9 years)	1) A carbohydrate–electrolyte beverage (5 mL/kg, 6.3% CHO, 18 mM sodium) 2) A capsule containing 6 mg/kg of caffeine 3) A capsule containing a placebo.	A first CHO beverage was consumed 1 h before trials and a second at the onset of each trial.	Two trials to exhaustion (TTE) at 90% VO2 peak and two 50 km time trials (TTD)	Exercise performance, metabolic parameters, alertness, cognitive performance and perception of trial substance were measured. Cognitive function included a computerized ANAM® test and Stroop word-color test.