Yeah a watering can that doesn't drip all over the office.
You really don't get it, do you?
I repeat:
Bonsai are NOT found at the office.
Learn about bonsai before you start designing anything for them.
What I'm hearing from here is that most people use just a regular watering can or coffee cup to water there Bonsai.
You have probably spoken with people that water their office ficus. You have NOT spoken with bonsai owners.
Seems you really don't understand the assignment you've been given - or the assignment is just plain wrong.
Did they really tell you to "to interview 3 people who own a Bonsai Tree
in an office space ?
In that case tell your teacher that when you asked real bonsai growers, they were very unhappy with the fact that he is propagating the widespread, but incorrect, idea of what bonsai is.
If you were given the instruction to design a pond for Koi, would you ask people about the goldfish bowl at the office?