Millions if not billions of people practice a form of fasting every single year. Ramadan fasting is probably the most known due to its religious factor.
Especially for those not consuming water, this is even more difficult and it truly puts a strain on the body's functions.
Athletes following Ramadan shall be planning ahead and be in an environment that supports them and puts their health first!
For an interesting review refer to the following article:
Cherif, A., Roelands, B., Meeusen, R., & Chamari, K. (2016). Effects of Intermittent Fasting, Caloric Restriction, and Ramadan Intermittent Fasting on Cognitive Performance at Rest and During Exercise in Adults.Sports medicine (Auckland, N.Z.),46(1), 35–47. https://doi.org/10.1007/s40279-015-0408-6
Shephard R. J. (2013). Ramadan and sport: minimizing effects upon the observant athlete.Sports medicine (Auckland, N.Z.),43(12), 1217–1241. https://doi.org/10.1007/s40279-013-0080-7