The 24-year-old singer started seeing the 31-year-old former UFC middleweight champion following her split from Wilmer Valderrama and the pair are keen to keep the romance casual for now.
A source told Us Weekly: "She's just trying to have fun right now. They've been talking, hanging out and hooking up, and they like each other.
"They're both having fun with it and enjoying it for what it is."
Meanwhile, the brunette beauty recently admitted she feels "free" since calling time on her relationship with Wilmer.
She said: "I feel really amazing. I feel really great and I'm growing. My life is just really, really exciting for me because I'm growing. It's new and fresh, and I feel free.
"I think I have so many people around me that I trust and that I talk to about things and they are the ones that are quick to tell me, 'Hey, you may be having a bad day but look at what you've overcome'. So that's what's really cool is to be able to surround myself with people like that."
The couple dated on and off for six years but announced in a joint statement that they had decided to call it quits.
They said: "After almost 6 loving and wonderful years together, we have decided to end our relationship. This was an incredibly difficult decision for both of us, but we have realized more than anything that we are better as best friends. We will always be supportive of one another. Thank you to everyone who has offered us kindness and support over the years. With only love, Wilmer & Demi (sic)."