in an affectionate or loving manner (`sweet' is sometimes a poetic or informal variant of `sweetly'); "Susan Hayward plays the wife sharply and sweetly"; "how sweet the moonlight sleeps upon this bank"- Shakespeare; "talking sweet to each other"
If you kick or hit a ball sweetly, you kick or hit it in the very middle of it so that it goes firmly and accurately to the place you are aiming for. He could strike the ball as sweetly as when he was 28 years younger. see also sweet