What edible solution can I cover bread in to make it waterproof? My partner and I are working an entrepreneurial project for school, and we decided to make a sort of edible water bottle.

We decided we would make it out of bread, which we would cover in some solution and leave to dry to make it hard and waterproof.

We considered using honey, but it would be too sticky, sweet, and expensive.

Is there any good solution that will make this bread waterproof and hard easily? Something that is cheap and not bad-tasting?

also, if you think this question should be posted on a different stackexchange site, please tell me.

Thanks.
Carnuba Wax. It's edible and waterproof. In my childhood they used to sell a candy bottle made of Carnuba Wax with colored sugar water in it. You'd bite the top off, drink the sugar water and chew on the wax until you got tired. 

http://chemistry.about.com/od/foodchemistryfaqs/f/carnauba-wax.htm