Working in hot environment such as kitchen restaurant can lead to dehydration and subjective fatigue which in the long term can impair the health of the workers. The following research was carried out to study the ability of formulated coconut drink to reduce dehydration and subjective fatigue of chefs at “X” restaurant in Semarang city-Central Java Indonesia. Formulated coconut drink was made of coconut water and formulated to contain 0,66 g/L sodium, 0,23 g/L potassium, and 7,6% reducing sugar. The coconut drink was given to the chefs at “X” restaurant in Semarang City, Central Java, Indonesia which was exposed to heat radiated from cooking in the kitchen. This study was a pre and post test control group design. Nineteen subjects were studied and their body weight, pulse rate, blood pressure, and temperature were measured before and after working each day for 6 consecutive days. The first 3 consecutive days served as control group and the second 3 consecutive days served as treatment group. Subjects in the treatment group consumed 2 x 200 mL of coconut drink everyday for 3 consecutive days. The first 200 ml were consumed in the morning before starting work and the second one were consumed in the afternoon at the break time. Subjective fatigue was measured at the first day and the last day of the study. Data were analyzed by Paired t-test, Wilcoxon, and Multivariate Analysis of Covariance (MANCOVA). The results showed that formulated coconut drink could reduce weight loss (p=0,003), pulse rate increase (p=0,008), diastolic pressure decrease (p=0,006), body temperature increase (p=0,004), and subjective fatigue (p=0,0001) of chefs working in the kitchen restaurant. When intake of energy and water for one day was added with the intake of the coconut drink, the drink still could reduce weight loss (p=0,0001), diastolic pressure decrease (p=0,032), body temperature increase (p=0,023), and subjective fatigue (p=0,006). Consuming 400 ml/day of formulated coconut drink for 3 consecutive days can give rehydration and reduce subjective fatigue of chefs exposed to radiated heat in a restaurant kitchen.