How large and how many pots are you using? I have to say that a cup of water per day seems like an awful lot of water for seedlings. I added just about 1/2 that to my recent sprouts and am paying the price right now. What are you using the sugar for? I do know that adding small amounts of sugar can promote beneficial bacterial growth, but I think that constant addition of sugar will be a but too much. Until you become familiar with watering and when to add more, you should consider an inexpensive moisture meter. I have recently purchased one and was a bit suprised at the moisture of my soil.