I must admit, I'm not quite "UL", more of a "pretty damn light (PDL)" hiker depending on destination and motives of the hike. But I learn a lot from this group/mindset.
But I stumbled upon this One Bottle Hydration system
that I tried and liked it enough to recommend it to a certain niche of hikers like me. It combines the hydration bladder tube and bite valve with the plastic water bottle approach. Really is the best of both worlds – convenience and reliability of a 28mm 1L Smart Water bottles (or wide-mouth nalgene 63mm) and the drinking hose from a hydration pack (less the awkward, hard to clean bladder). If you aren't a fan of hydration bags, hate reaching for the water bottle, don't like your water bottle strapped to your pack strap, and feel like you should be drinking more, its worth considering.
I recently took it on trip to Zion and really liked it, more than I thought I would. Definitely an item that will go with me on every backpacking trip I think. It kept me drinking more water and staying better hydrated than I normally would. Only down side (a good thing!) is I went thru more water than I normally do. And also kept me from having to reach for my water bottle from my pack's side pockets, which never come out easily for me.
Anyway, liked it enough to consider mentioning it.
Possible negative to UL: 3.5 oz (not an issue for me relative to its advantages).
Positives: just works, adaptable, keeps me drinking, no bladder, small garage-grown single-person manufacturer, fair price, and solved a problem I didnt know I had.
Happy hiking from Ohio