On 13 March 2014, she revealed to Complex that she had begun working on her second album with Weezer frontman Rivers Cuomo and Rostam Batmanglij of Vampire Weekend.

[19] Charli XCX further promoted the album by embarking on an eight-date UK tour in 2015, which began in Brighton on 24 March and ended in Birmingham on 2 April.

[32] Will Hermes of Rolling Stone stated that "Sucker is no retro gesture: Charli runs the album's rock & roll guitars and attitude through enough distressed digital production and thumb type vernacular to make this the first fully updated iteration of punk pop in ages ... Like so many of the pop pleasures here, it's a sentiment that just never gets old.

"[38] Miles Raymer of Entertainment Weekly commented that "SUCKER is pop-punk, radically redefined and dragged, middle fingers waving, into the future.

"[3] Brian Mansfield of USA Today wrote, "On Sucker, XCX doesn't just tweak the ear-candy pop template, she blows it up, then pries the shiniest bits from the asphalt.

"[40] At AllMusic, Heather Phares opined that the album's "mix of youth and sophistication is more than a little volatile, and sometimes it feels like XCX is still figuring out what really works for her music ...

"[39] James Rainis of Slant Magazine viewed the album as "the sound of a long-incubating star emerging so fully formed on an international stage that it's difficult to figure that an artist gifted with so much sneering bravado was ever thought of as an underdog ...

Someone needed to author the aural equivalent of the body shot, and Charli XCX has provided the platonic ideal of just that: a party album charged equally with punkish rebellion, hip-hop cool, and pop universality.

"[41] Jamieson Cox of Pitchfork felt that "Sucker isn't an endpoint for Charli ... and it's not her finest work, but it's plenty good enough to rope a cohort of new fans into what's promising to be one hell of a creative ride.

"[6] Jon Pareles, reviewing positively for The New York Times, emphasizes "Sucker is far more direct; it's smart, loud, cheeky, gimmick-loving pop, intent on making every song go bang ...

"[42] In a 2024 cover story for Billboard, Charli told Kristin Robinson that "she considers 2014's Sucker, for instance, 'an attempt at what Olivia Rodrigo's Sour was able to do much better.

"[44] Spin ranked it the sixth pop album of 2014, commenting that "Charli's second full-length shaves off the densely layered atmospherics and dreamy soundscapes.

[46] Sucker debuted at number 28 on the US Billboard 200 with first-week sales of 28,907 copies, making it Charli XCX's first album to enter the chart.