Food is not a priority for short term survival. A pocket sized container does not offer much room for luxury.
For a small or medium sized kit my answer would be zero. The room could be used for more imoprtant things like matches, water purification or water containers. In a medium sized kit, Iīd rather include a space blanket. That will save more calories than the same volume of boullion cubes can provide.
Boullion cubes should be kept cool for storage. Carried on the body they tend to go bad fairly fast and they sometimes leak some fat too. IMHO itīs just not worth the hassle.
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If it isnīt broken, it doesnīt have enough features yet.