1 = correct
2 = unnatural but could be used
3 = for a drink of coffee into a cup etc it is incorrect
3 = for a pile of loose tea, or tea bags, or tea that is not liquid it could be used.
If you have a full cup of tea leaves in a cup you could put some sugar on the tea.
In the tea or anything that makes the sugar dissolve. Or on the tea where the sugar does not dissolve.