Backpack Bottle Sleeve

My kindergartner was having trouble putting his water bottle in his backpack sleeve. The rubber on the bottle was preventing it from sliding into the pocket nicely. This fits into his L.L.Bean back pack sleeve and holds it open a bit so he can easily insert and remove the water bottle!

Ive made a few different shapes, some were too solid, some were too flexible. This hexigon shape seems to be strong enough to survive his abuse.