You could feed one carrots and clovers to one rabbit and feed regular feed to one and report how different they act if you have two.
I'm doing the same thang so I don't know
You can somehow test the rabbit's memory or if you have two you can see if the weight of the rabbit affects how high it can jump.
You can see what they make with there fur.machines that has science
See how much methane is in rabbit crap. Hehe. I'm doing that one