For my homemade Jager bottle costume I took a box and cut out the arms and head area to my size so I could fit into it and wear it comfortably. Luckily my dad is a contractor and he was able to add chambers on the inside with the nozzles that actually dispensed Jager on the sides.
We took a black garbage bag and glued it onto the box making sure to keep it as smooth as possible while attaching to the box. We took a real Jager bottle and blew up the Label and the Government warning on the back and then glued it onto the box.
I also made a hat with construction paper that was white trimming glued to it and added the label to the top of the hat to make it look like the bottle cap. It took a few days to get this homemade jager bottle costume ready and it was cheap to make!