*On a normal 15-20 mile weekday ride I'll just have a glass of water before and then drink water as needed after riding.
*Longest ride I've done recently is 35 miles. I drank a big glass of water prior to riding, took a bottle with me and drank most of that on the return trip (out-and-back ride), then drink water as desired when I got home. Temp was about 80F.
*If I was out for an all-day ride I'd drink water regularly and err on the side of too much.
*I don't have prostate issues and I don't use additives in the water, nor do I drink Gatorade or energy drinks.