Step 4: Attach the Cup

Picture of Attach the Cup
If you've made the loop in the crook tight enough, you don't strictly need to use epoxy, but it's an extra bit of assurance that you won't spill your drink. 

Run a bead of epoxy or jb weld (I use E6000 for nearly everything, it's all kinds of awesome) under the lip of the pencil cup.  Then put the cup in place at the top of the reshaped crook. 

Allow that to cure overnight, hit it with the spray paint to cover up the dings you've left in the soft metal, and you're done!