What we're drawing
Cans of soda behind the glass, a slot for cash, slots on the side and a glowing light on top. The light comes from the top front, so the top is a bit lighter than the side, the bottom is the darkest, and the edges catch some light.
Step 1: Outline

Pick any dark color. Draw an isometric line of about 15 pixels and a 6 pixel line at an angle to it, like a tick. Copy that angle, flip it and place it to close the top, with one pixel of space on each side. Draw the front edge straight down, 26 pixels, then copy the top and move it down for the bottom, joining it to the vertical line.
For the glass, count 17 pixels down from the top and outline the front. Erase the edges you don't need.
Step 2: Colors

Fill the machine with a dark grey, the glass with blue, the inner edge of the glass with a darker blue, and the stripe under it.
Step 3: Shading

The bottom part and the side are darker than the top. Take the darkest shade and darken the lower part of the machine. Use the same color to cover the black line there.
Step 4: Highlights

Now the edges, each with its own brightness. The front edge is the brightest. The back edge is bright too, but less. The bottom edges are darker still. The top edges are so subtle you barely see them. And the top front edge becomes a glowing lamp in plain white. Then give the top of the machine a slightly lighter shade than the side.
Step 5: Details

The cash slot goes two pixels below the glass, in the front edge color. The side gets three slots of 21 pixels, one above the other.
And the cans. Each can has three parts: a dark part, a lighter part and a top, all following the isometric angle. Draw one, then copy it and stack the copies along the isometric line. Select the whole row with the magic wand, copy it, and paste it again with one pixel of space. Row after row, the machine fills up.
The finished machine

It's one of the pieces of the isometric arcade building in the course, next to the air conditioner, signs and balconies.