As the above answer states, you just need references to your bottle actors in the level BP, that is one thing it is quite handy for. If you need to communicate with the level BP which I think is what you might be asking for by asking how to “cast to” you are looking for an event dispatcher. That will allow you to fire off events in the level BP when things happen in world actors like your bottles. If you need help with casting, references or event dispatchers check out videos #1, 25 and 26.