Two answers - the practical answer, and the actual science answer.
First, for practical purposes, powdered Koolaid mix will raise a person’s BG just fine even if it is concentrated. Having it more concentrated won’t be the fastest, but as long as EH is not extremely dehydrated and not doing extremely strenuous exercise, he could eat the powder straight from the bag and it would raise his BG.
But a more exact answer is that eating the powder straight, or drinking it in a more concentrated form would be slower in terms of absorption.
Osmolality is a measurement of the concentration of a fluid, in terms of the number of solutes per volume of fluid. The osmolality of the blood and body fluids is approximately 290 mOsmol/L.
A hypotonic solution is any solution that has a lower pressure than another solution.
Hypertonic solutions have an osmolality higher than the body (> 300 mOsmol/l)
Hypotonic solutions have an osmolality lower than the body (< 280 mOsmol/l) which actively promotes fluid absorption.
Isotonic solutions have an osmolality similar to the body (= 290 mOsmol/l)
Next is “tonicity”…
Tonicity is the ability of an extracellular solution to make water move in or out of a cell by osmosis. This determines what direction fluids flow across the membrane. Water wants to flow from areas of low concentration to high concentration. Your body wants to keep things equal.
Sports drinks are big business, and the idea is that you want the drink to be absorbed faster. This becomes especially critical during extreme endurance or intense workouts.
So simple answer is - it’s just fine, drink it concentrated and it will work as long as he’s not extremely dehydrated.
But the more exact answer is - having it more concentrated will be a bit slower.