A cheap Kuyou knockoff 2 liter hydration backpack, cost about $15-$20. Works fine.

I used it once in summer 2020 when I first got it, for a 50 mile ride with no nearby convenience stores, etc., on the hottest day of the year -- peaked at 113F. I also carried a couple of insulated Camelbak bottles. Worst part of the ride were the two flat tires with no breeze, and no shade on the first flat (found a tree for the second flat). I probably drank half my water on those two stops. I had about one swallow remaining by the time I got home.

Leaked a little at first until the O-ring settled, then no problems. The leak was very minor, just enough to cool my back but not enough to waste water. No leaks since that first time. And the bite valve took a little getting used to but works fine now.

And the bladder and hose left that plastic-swimming-pool kinda odor and taste at first. I filled the bladder with water and baking soda and let it sit in the fridge for a few days. No noticeable odor or flavor after that.

I've used it several times this summer, mostly jogging and walking 3-10 miles per session. Very handy. Stays put well enough while I'm jogging. Has enough padding/insulation to keep the bladder cool for at least a couple of hours. Two inner pockets with zippers, enough to hold a few gels or snacks in one pocket, and my wallet, keys, etc., in the other. And a mesh outer pocket for stuff like my bandana, face mask in case I needed to go in a convenience store for refills, etc.