The two also held hands, taking a stroll on the sidewalk.
The pair bought coffee and window-shopped around the Le Marais district, an eyewitness tells ET of the casual outing, noting that "there was a lot of kissing going on between the two, and they were both in very good moods. It was just the two of them as they strolled through Paris."
Stewart and Sokolinski -- who's better known by her stage name, SoKo -- have been spending plenty of time together recently. The two were first spotted looking affectionate with one another during a lunch date at Cafe Gratitude in Los Angeles earlier this month, and on Sunday, Sokolinski sweetly greeted Stewart at the Charles de Gaulle Airport in Paris with flowers.
Although both Stewart and Sokolinski have never confirmed they're dating, the "We Might Be Dead by Tomorrow" singer has made no secret on social media about having a long-distance relationship.
"Spending every minute of my days and nights loving her from afar," Sokolinski tweeted last Wednesday, linking to a picture of herself using FaceTime.
Sokolinski, an accomplished musician and actress in her own right, has opened for both M.I.A. and Foster the People. She's been upfront about being bisexual in the past, telling After Ellenin June 2013, "I've liked girls since I was f**king born."
"I mean, I’ve always been dating girls," she said in the candid Q&A. "For the last year, I’ve been dating girls, but it doesn’t mean I won’t date guys again. It just means, I like the ladies better."
"If you feel like you really want to define yourself, and you have the ability to articulate those parameters and that in itself defines you, then do it," Stewart told Nylon magazine. "But I am an actress, man. I live in the f**king ambiguity of this life and I love it. I don’t feel like it would be true for me to be like, 'I'm coming out!' Until I decide that I'm starting a foundation or that I have some perspective or opinion that other people should be receiving… I don't. I'm just a kid making movies."
"Google me, I'm not hiding,” she added. "I think in three or four years, there are going to be a whole lot more people who don’t think it's necessary to figure out if you're gay or straight. It's like, just do your thing."