Bottle drilling bit
This is the bit you would need to drill the hole in the bottle bottom to construct the bottle walls. It is the size for 3/8″ rebar.
Always submerge your bottle in water when using this bit. I use a drill press, and submerge the bottle in a bucket of water, filled just enough to cover the bottom of the bottle. Don’t force the drill, just ease into the bottle, holding secure with one hand.
Used properly, this bit should last to drill easily 100 bottles.