Lots of dried foods like ramen, beans, mashed potatoes, etc will hydrate without hot water. It takes more time, but works well. These no-cook setups are used by many long trail thru-hikers that choose not to bother with stoves and fuel.
I actually hiked with a person who "cooked" or rehydrated meals by putting the ingredients in a sealed plastic bag and then putting that in his underwear. Seriously.
Perhaps a clever, yet obviously comedic, idea. But which foods will cook at a warm temperature that wont at a cold?
There is no cooking involved in those cases, just rehydration. It just happens faster at higher temperatures. And it's less unpleasant than eating ice-cold.
Yes, I should have used prepare in place of cook, as cooking requires heat.
Ah, the infamous crotch pot slow cooker.
Wouldn't bacterial growth be a concern in a wet, warm environment for an extended period? Even if the food was bacteria-free, the container can pick things up from the environment. Even if it's low-risk, on a long thru hike I wouldn't want any risk of stomach issues.