This was a trick I decided to adapt for a small party I was throwing. These days, every cocktail enthusiast and their grandfather has a spherical ice mold. I saw a trend for hollowing them out and serving a cocktail inside the ice sphere. I just did my own variation.
You only need a little equipment for this. You'll need a freezer, naturally. You'll also need a heat source and a metal point to heat, though a soldering iron does the job brilliantly, provided it's clean. You'll also need a small funnel, though a syringe or meat injector works a bit faster, and when dealing with ice, speed is critical. Lastly, you'll need a spherical ice ball mold that you can flip upside down and remain stable. I prefer the style pictured. The only other things required are the liquids, Jagermeister, and Red Bull.
The basic premise is that ice freezes from the outside in. The trick is just stopping it before it freezes too much. Fill your ice ball mold with water, add the top half, and put it in the freezer. After an hour and a half, flip the mold over. This allows the ball to freeze evenly as different parts of the freezers have different temperatures. Also, any air bubbles and impurities would float or sink, throwing off the thermal conductivity. Otherwise, slices of the ball would be fragile and others very thick. After another hour and a half, remove the partially frozen ice ball. Bear in mind that these times are relative to what I find to be the average home freezer. You may need to extend the time.
Rinse the outside of the mold with warm water, not hot, or you may crack the ice. Now, we need to hollow out the mold. Heat an ice pick or use a soldering iron to poke a hole in the top of the ice ball. Draining can be a tricky part. You can flip the ball over and drain it out, but it will take ages because of the lack of airflow. Using a meat injector seems to be the fastest way of sucking out most of the liquid. You can also use a straw and blow sharply into the ball to eject a good portion of the ball's water while it's upside down to drain it much faster. However, this technique isn't suited to a bar environment.
Next, using a funnel or the meat injector, fill the ball with Jagermeister. Plug the hole with something that allows the ball to stay upright. A cherry with a pick through it works well, as could a coiled citrus twist. Add the ball to a large rocks glass and fill the glass with Red Bull. Serve with a small hammer to let the guest smash the ball open.