Be carefull, don't eat to much ice cream. It's a delicious reward, but has to much sugar and grease.
I don't reward my self or establish these kind of goals. It gets frustrating, checking the time to much frequently. I prefer to decide the amount of things and what I want to study, regarding the time I take to do it, I think it's more productive.
I don't think there is a reward that would get me motivated...being late and having a lot of things to study is my drive.