Drilling holes in glass and porcelain is a lot easier than you might think. I had to drill holes in the bottom of 30 coffee mugs so that they could hold succulents and be able to drain the water.
This process is messy so make sure you do it outside. I used a hose as my water source so that it was constant and cold.
Make sure you thoroughly wet the cup before you do any drilling. I would also do this over a towel since there will be porcelain dust.
Next pick whatever drill bit you want for the drainage hole. Since the cup is now nice and cool and wet you can drill out the hole. You dont want a lot of pressure becuase that cold break the cup. Slow and Steady wins the race.
The main thing is to keep the cup cool!
Once you have drilled the holes you can plant your succulents. These make really cute gifts or decoration for your house.