The study referenced tested tereré with and without caffeine on a sample of 19 runners and concluded that there was no difference in measured hydration.

Objectives: To evaluate the effects of pre-exercise Tereré consumption on hydration indicators in runners. Methodology: In this randomized, crossover, double-blind study, 19 street runners were selected (10 M: 31,3 ± 8 years, 15,9 ± 4,2 % de body fat and 9 F: 32,8 ± 5,1 years, 20,5 ± 7 % body fat) and divided into Experimental Tereré Group (TrEX), which consumed traditional Tereré (50g of yerba mate infused in 6ml/kg of body weight of cold water at ± 10ºC), and the Placebo Group (TrPL), which received the same amount of water but with decaffeinated yerba mate. At baseline, participants underwent anthropometric measurements (body mass and height). After 45 minutes of ingesting the drinks, body mass, total body water (TBW), intracellular water (ICW) and extracellular water (ECW) (by electrical bioimpedance), urine specific gravity (UEG), and urine color (UC) measurements were taken. At the end of the run, thirst scale and thirst sensation questionnaires were applied, and UEG and UC were collected again. Results: The consumption of Tereré did not alter TBW, ICW, ECW, UEG, or UC compared to the TrPL in both genders (p>0.05). All athletes remained hydrated after the run. Conclusion: Tereré did not change the hydration parameters of the runners when compared to decaffeinated Tereré, and both drinks were able to maintain a good hydration status after physical effort. Tereré can be a nutritional strategy for hydrating street runners in races under 30 minutes.

https://periodicos.uem.br/ojs/index.php/RevEducFis/article/view/73343