We just have 2 more class sessions in our study of glass. This is a pretty terse 16"x12" and I am painting on my favorite ground - a scraped down canvas; the remains of maybe 10 scraped off paintings. It is the only way to give the canvas that wonderful crapped out look; almost a shame to cover it up.
Our little green apple makes an appearance but only as a subordinate; having an item BEHIND the glass object helps show clarity, especially if the background is ambiguous.
Though it has nothing to do with glass, I would note the brushes inside of the mug. It seems obvious that they would have to rest on the rim and as well, go to the bottom; sometimes this is lost on the beginner (or some of us who can't make our brushes straight). Any straight item, be it a brush, pencil, stick, flower stem cannot stand on its own but must rest on the rim and (allowing for a bit of glass distortion) must also follow a straight path all the way to the bottom of the container. So check that angle in the drawing before heading to paint.