Gookinaid is now called Vitalyte.
The purpose of Vitalyte is to replenish blood electrolytes and to increase blood volume, not to treat magnesium or potassium deficiency.
The concentration of electrolytes in Vitalyte is identical to the concentration of electrolytes in the blood. This helps the fluid to be absorbed by the body more efficiently than plain water, thereby increasing blood volume without altering blood electrolyte concentrations.
Whether this is “more effective” than taking electrolyte supplements with plenty of water, probably depends upon what your exact purpose is.
Hope this helps.