Hi bikesforever, welcome to the forum.
I have been lucky enough to not have to deal with UTIs (at least not so far), so there's only so much I can offer. But fwiw, I try to drink about one water bottle per hour when I'm on my bike, which is about 20 oz. According to the label on the Diet Coke that I am drinking right now, 500ml = 16.9 oz. So I try to drink a bit more than what you're getting. Note that I ride for fun and exercise, not commuting or transportation, 90 min - 2hours (15-20 miles) during the week and 2-6 hours (30-65 miles) on the weekend.
I don't know what the climate is where you live. We have hot summers here. So during summer rides if I'm drinking less than 1 bottle in a hour I will chug when I get to a rest stop, which is usually every 1 - 1.5 hours. This seems to be sufficient for me. In cooler weather I probably drink a little less because I'm not sweating nearly as much. As annoying as it is to have to pee during a ride, it is not something I try to avoid because becoming dehydrated can cause more than enough problems. I also ride often with older men who need to stop pretty often, so we try to plan bathroom stops into the route every 1-2 hours. Ideally these stops are at convenience stores, community parks, grocery stores or fast food restaurants. If necessary we will go behind a tree, though it's not always easy to find one with sufficient privacy.
I generally alternate between plain water and Gatorade; I'm not aware of sports drinks contributing to UTIs, but I've never done any research in that area. If you're getting that jello feeling in your legs then you are bonking -- running low on blood glucose. I understand not wanting to eat during a ride, because my stomach doesn't handle food well either, especially on hot days. But with trial and error I've found some things I can tolerate, like carbohydrate gels (Gu or PowerGel), Jelly Belly sports jelly beans, cereal bars and fig bars, Honey Stinger waffles, crackers or pretzels for salt. I will force myself to have 200-300 calories at each stop whether I am hungry or not.
- Gray Trek Madone 4.7 road bike, mystery crack in top tube repaired by Calfee, Bontrager Affinity RXL saddle
- Red Trek 6000 mountain bike, Bontrager Evoke WSD saddle
Gone but not forgotten:
- Silver Trek 2000 road bike
- Two awesome and worn out Juliana saddles