Hydration Efficacy Index (HEI) is the score of hydration level of drink items in the game. It was originally created by a team of nutritionists at the University of Jalan to compare the effects of beverage choice on hydration levels during long haul space flights, and was adapted by UEE Health Services as the standard measure by which various drink selections can be compared. By considering such factors as moisture retention, absorbency rates, osmolality, caloric count, and electrolyte levels (specifically sodium and potassium), a beverage can be graded using one standardized index. The higher the score, the more effective the beverage is at keeping the consumer hydrated for longer. Substances like caffeine and alcohol have the potential to decrease the index score by increasing the rate of water loss from the body.
Standard filtration system water has a baseline score of 80.