Pocari Sweat is 67g/L of sugar and 490mg/L. This is on par with western sports drinks like Gatorade(59g/L sugar, 523mg/L sodium)or Powerade (57g/L sugar, 409mg/L sodium). This is less sweet than typical sugary drinks which can be 10-15% sugar, but normal for a sports drink.
Sports drinks certainly help if you are sweating moderately, but are inadequate for intense exercise in the heat. When you are sweating intensely (>1L/h of sweat), you can lose sodium at over 1000mg/L. Supplementing sodium and other electrolytes may be necessary.