Start by drawing the bottle cap first. The following steps will show the entire process of drawing the bottle cap.
The bottle cap can be a bit more detailed than we'd like to expect. If you need to, you can look at a real bottle for a better reference.
Now that we're finished with the bottle cap, it's time to start drawing our actual bottle.
Draw the top part of the bottle. Basically two vertical lines going down from the bottle cap.
Next, draw the rest of the bottle all the way down to the base. Each side o the bottle should be as symmetric as possible.
Lastly, to give your bottle an extra transparent appearance, draw parts of the other side of the bottle. Notice how you can see the interior base of the bottle in this drawing. The bottle now looks more solid this way.