Miley Cyrus. Picture: Supplied/BangShowbiz

Miley Cyrus' younger sister Noah "spit" in her mouth when they performed together last month.

The 24-year-old singer shared the stage at the iHeart Summer '17 Weekend with her younger sibling Noah last month and though she initially had "fun" with the 17-year-old pop star, she admitted things took a grim turn when they got carried away playing with water pistols.

However, the 'Wrecking Ball' singer wasn't too upset because she admitted Noah had learned her mischievous behaviour from her.

Asked what it was like to perform with her sister during an Ask Anything chat with iHeartRadio, she said: "We had fun, we played with water guns, we kind of sang with each other, but afterwards... she spit on me. 

"She actually spit in my mouth as I was speaking.. so that wasn't fun. But she learned that behaviour from me."

The 'Malibu' singer also revealed she is very keen to stage an exhibition of her own artwork in New York.

She said: "I'd love to come to New York again and be able to show my art in an actual gallery. That's something I'd never done before, so I'd love to do it again."

Noah recently admitted she is "proud" to be Miley's sister and get the chance to hang out with her at big events, but she isn't thrilled by the comparisons between them.

She said: "I'm so proud that Miley is my big sister, and to be able to go to these big radio shows and hang out with her. Of course no one wants to be compared to another person. But it's like, if a person can only see me for my sister, then that's really their problem."

The 'Make Me' hitmaker - who released her debut single featuring Labrinth in 2016 - also revealed her famous dad Billy Ray Cyrus could have a song on her forthcoming record.

She said: "Hopefully it will be done by this fall. I worked with so many amazing co-writers and producers on it. My dad might have a song on the album. I'm so blessed for this whole thing. I worked with some really talented, experienced writers."