Kolak is sugar water with coconut fat and some fruit in it, and the fruit is the smallest number. 100g of kepok banana is about 90 calories, 40g of sweet potato is 45, and the kolang-kaling is 20. That is 155 of fruit and root, all of it fine. Then 120ml of santan at 110 and 35g of gula merah at 125. The liquid is 235 calories and it is the part people drink from the bowl at the end.
During Ramadan this is the first thing in after 13 hours of fasting, and the timing is the problem, not the kolak. A 390 calorie bowl, then es buah, then three gorengan, then a full dinner, then more at sahur. Kolak on its own is a reasonable dessert. Kolak as the opener to a 2,000 calorie evening is why people gain weight in the fasting month, which surprises everyone every year.
The versions matter. Kolak pisang ubi with thick santan from a warung is 390. Kolak biji salak, the orange sweet potato dumplings in palm sugar syrup with santan on top, is about 320 because there is less santan in the base. Kolak candil (glutinous rice balls) is similar. Bubur sumsum with kinca is lighter still at about 250. Kolak labu (pumpkin) is the lightest because pumpkin is mostly water, around 280.
At Rp 8,000 to 12,000 a cup it is cheap, and a 120g plastic cup is only 196 calories according to FatSecret. The trouble is the bowl at home is 300g and the pot is on the stove all evening.