Do d-rations make good survival rations?

The soldiers and aviators, airmen and parachute jumpers did use D-rations for emergency purposes so they would keep up their blood glucose. The D-Rations consisted of chocolate bars, candy, vitamins and gum. The men said they were real life savers on the long hours in the planes and when they ran out of K-rations. Some of the airmen would also grab Sandwiches from the mess hall to use with the D-rations. Some managed to get thermoses of coffee too.