This is a quick easy solution, and might possibly be the best instructable of all time, all in One Step!
Step 1: Stop the Insanity!
But there is an easy fix, instead of pulling the tab back as in the first picture, you need to push the tab into the cup. My father and I were enjoying coffees at Tim Horton's one day, when he let me in on this little secret, he is a genius, jack of all trades.
Just look at the pictures.