One of the great things about canoe camping is that you can bring a nice big cooler with you and enjoy refrigerated food and drinks for the first few days of a trip. Not so with sea kayaks, where everything you carry has to fit thru a hatch.
Up until now I’ve nested two six pack sized soft sided coolers, frozen as much of the food as possible before hand and packed with ice the morning of. There is still some ice left the first night and the contents are still reasonably cold the second. After that it becomes my garbage can.
I tested this one gallon thermos-style bottle; it looks promising and I’ll use it next trip.
https://www.amazon.com/dp/B0BB5W6QKP
The thermos is 3 1/2 pounds and seems rugged. I can fit my hand in the opening.
I tested with 12 oz beer cans. I still had a cold beer after 3 1/2 days. Details of the test: Room temp was constant at 69 degrees. The thermos started at room temp. I loaded three cans of cold beer upright on the bottom, then packed big clunky ice cubes from my fridge around and between the cans. Then I laid a can horizontally and packed in as much as I could around that.
I left the thermos vertical during the test. After 12 hours I removed a can, and then removed another every 24 hours after that. Those were the only times I opened it. I did not remove any ice water. There was still ice with the third can. No ice left on the fourth but it was colder than my fridge.
Results would have been better with crushed ice. My packing-challenged cubes melted down to 3 1/3 cups of water, 27 oz. Probably would have gotten double that with crushed ice, and result would have been better if I filled around the cubes with ice water. Not sure if laying the thermos on its side would have given different results.