or just say "I've been in a hot air balloon once." if you mean to say you've had ONE experience in a hot air ballon. Or you could say "I've experienced hot air balloons." or "I've been in hot air balloons." if you mean you have had multiple experiences in hot air balloons. People do not really need to be told you experienced hot air balloons, unless you are talking about familiarity (learned skill and history with a subject). For example I'm an experienced teacher. (I'm implying I've done it before, and it is not new to me). Thus if you were a sea captain you would say you have sailing experience. Everyone would know what you meant if you said "I've been in a hot air ballloon before." However, saying you are experienced in it, kind of implies you do it as a job. Unless you are talking about a great experience you had, then experience is like a memory, or important life moment. I'm experienced with something implies that you know how to operate it. I'm an experienced pilot (oh so you know how to fly airplanes). I've been in a plane before (oh you were a passenger).

1) is correct. 2) is technically correct, but sounds a bit awkward. 3) is incorrect. You could also say: "I've had experience being in a hot air balloon."