Proper hydration stands as a cornerstone of cycling performance, particularly during hot weather rides when choosing between bottles and a cycling hydration pack becomes crucial. Cyclists can lose between 500-1000ml of fluid per hour through sweating, depending on temperature, humidity, and intensity. This fluid loss directly impacts power output, endurance, and cognitive function on the bike. 

https://www.pacelinebikes.com/bottles-vs-cycling-hydration-pack-cycling-hydration-101/