I use one cup of white sugar to a gallon of warmish water for the first six hours or so then I pour it out, rinse the waterer and use plain water with a bit of electrolyte/vitamin solution in it.
The sugar serves to get a few immediate calories into their systems but it's not something you want to leave in their forever. After the first few hours they should be eating their starter and getting what they need from digesting that.
.....Alan.