Hi,
There are some mechanical limitations at work. Protein and carbohydrate each offer 4 calories per gram. Both have about the same density as far as I can see when dealing with whey protein isolate powder (83% pure) and pure carbohydrate powder such as malodextrine. Fat has more than double the calories at 9 per gram but surely more dense.

so drinking pure olive oil gets you the most calories per volume but likely to create some digestion issues. On the other end just simple protein powder mixed into liquid with milk or water offers the ability to adjust the caloric density to what works best for your situation. don