Magnum bottles(https://www.amazon.com/Zefal-Water-Bottle-Magnum-Clear/dp/B003WOEU9S/ref=sr_1_2?dchild=1&keywords=magnum+water+bottle&qid=1617965029&sr=8-2)
can be one way. they are not insulated and are the same dimesional size as an insulated 750ml bottle.
my setup for long rides with no chance for refill is this.
3x1L bottles with double servings of Carbo Rocket(660 Cal/bottle) My bike runs 2 bottles in the frame and 1 on the bottom of the downtube. typical road bikes won’t have that 3rd locations so you’ll be limited to the 2 bottles.
Then I run an Orange Mud Endurance hydration vest with a 2L bladder, filled with pure water, no mix.
Unless its above 80, this setup plus other on bike snacks, is good for a solid 10-12 hours. With only 2 bottles, I could go for around 8 hrs.