Here is a sketch I did to practice a bit of “negative” space just to do something different. I usually sculpt with Dynamesh by “adding” geometry but I tried doing the opposite with this one.
I started with the shape of the bottle (simple primitive subdivided). I used the Dam_standard_brush to define some of the big areas I was going to “carve” in, then I started to subtract geometry with BuildupClayBrush (holding alt) while “Dynameshing”. towards the end I use the standard brush and inflate for wrinkles and other details.
here is a time lapse of the process: