JEI doesn't show recipes for almost all the drinks like the Nitrogen Pack, Lemonade Pack, Soy Milk Pack, Sulfuric Acid Pack, Cream Drop, etc.

is this intended? or simply these objects don't have recipe at the moment?

There are no recipes for those items.
Paper packs are fluid containers and can be filled with HaC fluid using tanks and fluid slots.

oh ok, then i think it would be good to add this info in JEI. (when they press "R" to access to the recipe this info could be displayed)

We are currently working on a JEI plugin that will display all fluid information (temperature, unique dictionary of HaC's and drinking effects).
Drinking effects are also shown in the tooltip of the item (as well as many other mod items) and it's visible in the JEI item list, we won't make a drinking effect-only JEI plugin.