Since my bike came with 2 bottle cages, I just use those. I do prefer to get a wide mouthed bottle so you can get ice in it. I just use the freebies that come with ride swag bags as long as they hold 22-24 oz. They get grotty and dirty out on the road so I keep four of them in circulation. 1 in the freezer with plain water being frozen for the next ride, 1 of plain water on my bike, one of electrolyte on my bike and one being cleaned with denture cleaner.

I have found that the insulated bottles are a waste of time around here, the stuff still gets warm. Even a fully frozen bottle only lasts about 10 miles before it is thawed although still cool. Gotta love the heat and humidity around here.