So a while back, I created a plastic bottle in Photoshop. At the time I wasn't sure how to render a bottle in Photoshop, but I gave it a go. Although I never kept the the original photo, I created this bottle by taking a photo of a plastic bottle and then simplified the reflections.
First I created a plain background with a grid of dots on it so that the transparency of the bottle would be shown.
Then I traced the complete outer shape and filled it with a sold grey. Then, using the eraser, in airbrush mode, I took away some of the middle area to show some transparency in this base layer.
I then duplicated that layer and brightened it. Then I took the brightened layer and airbrushed away all, but the outer edges, just to give the bottle some shape.
The reflections took up the majority of the time in this project. It is just a case of tracing almost all of the reflections, by drawing a path around each one, filling and blurring until it looks realistic. The point of this is not to make it look exactly like a photo, but a simplified version, so that if you have to add a label design to your image, it looks better than a digital photo.
To get the red of the bottle top, I just copied and pasted the layer and then hit the "colorize" button within hue and saturation. Then I brightened it to get a vivid red.
Added some reflections to the bottle top.
Finally I created a bottle reflection below the bottle, to stop it look like it was floating. To do this I just merged my layers and duplicated the bottle, flipped it round and eraser airbrushed away the edge. Done.