It's getting warmer and I'm getting older. I already work in a hotbox of a warehouse where I sweat a ton during the Summer (most of the job processes can be relocated into the a/c part of the facility, but not mine ). I've got two cages already, but am hesitant to use the 2nd one. In the pic below, that position was being used by a bottle that I had stored my flat kit and multitool in, but have since relocated those to the wedge pack.

It gets warm enough here where if you don't take in some fluid at least every 15 minutes it can lead to issues. Ideas?

I would start with a 24 ounce insulated Polar bottle. I like mine a lot. Are there no braze ons for another cage on the seat tube? Aside from that, you could strap a bottle or two to your rack, then stop and swap them out when necessary. You could to the same with the cages you have, just switch the full one to the cage that you can reach.

No bosses on the seat tube. Actually, I've got my cable lock w/QR mounted on the seat tube. And I could just switch out bottles, but my primary concern is that of dirt/debris hitting that lower bottle. Had a different commute route that involved gravel roads/crushed rock and the amount of dust that hit that bottle was rather unsettling. I prefer to drink and not chew.

https://www.performancebike.com/bikes...1545500_400163

Get a Camelback and all your hydration problems will be solved.

get a water bladder. they are awesome.

I have a couple of Zefal bottles that came with a flip off cover. I think one of them broke pretty quickly, but I'll bet someone else makes them, maybe more durable.

There are 500 different ways you could carry water on the rack sitting on the back of your bike. You only need access to one water bottle at a time.

Thought about that one before, but then I'd have to move the contents of the seat wedge to somewhere else, as I don't think it's possible for the two to coexist.

And hydration bladders may be nice and all, but a) the cleaning process looks to be a chore and b) I'm really trying to free up my back to allow air to flow more freely over me.

+1 on the Polar bottles. I carry 4 of them, 2 in cages and 2 more in panniers w/ damp towels around them. 3 hours later and I still have bits of ice in 'em.

Hard to believe the OP's seat tube doesn't have bosses on it! That sucks. The bottle on your bike doesn't look much smaller than a Polar bottle, you may be able to fit one in there. I ground the side & top lid on one of mine putting it in the low cage like yours. I didn't have fenders on a suspension fork bike, hit the front brakes and drove the bottle into the wheel. Watch out for that! You have fenders so you ought to be safe.

Before I bought my new bike & panniers I had a Topeak Explorer rack with the big MTX trunk bag. That thing was great for carrying water, like 5 or 6 bottles! Get that many in there and it was a bit top heavy, but it got the job done. It was insulated, too. Wrap a few of those soft ice packs around the bottles and you're set.

https://www.amazon.com/Topeak-MTX-Tru.../dp/B000FICAQ4

Zefal makes Liter bottles. and a gizmo, a plastic hose clamp like mounting scheme..

.. from '2 Fish', a velcro strap on cage. back of the Fork blades will take 2 more cages

Got one of those Zefal gizmos to mount a cage to the bars and I broke during the install.

Mounting to the fork blade... a la the Salsa Fargo...

I've got access to duct tape, zip ties, and a spare cage (from the Zefal debacle)....

Camelbak bladders are easy to clean, provided you only use water in them. Their convenience is well worth the cleaning really, because there's no other easy way to add 100oz of water to your bike. I'd get a Camelbak and a frame bag (like the Jandd or Relevate Designs Tangle). This way you can mount the 100oz water bladder on the bike when you wanted to, but still have a nice camelbak backpack for hiking/fishing/whatever.

Last Summer, I would stash two frozen water bottles in a trunk bag (the kind that would fit nicely on your rear rack. After a few hours of riding in the 90-95+ Texas heat, I would still have to pull a bottle out for quite a while so it could thaw enough to drink. It was so worth the weight penalty. My current bike's rack doesnt accommodate a trunk bag - still working on what I'm going to do this year...

Two fish makes cages that will strap to a seat post or down tube, there are also ones that will attach to your stem cap.

I use a camelback for long training rides. I find that the cold water (and it stays nice & cool realy long) keeps my back cooler, and this is in 90+ degree Florida. Much different than the backpack that I carry to work which seems to increase the temperature by 5 to 10 degrees.

Plus, your drinking source is always much cleaner than a bottle in a cage. This is one of the reasons why they are so popular with mountain bikers.

https://www.showerspass.com/veleau