As a youth player, Sander played for a local clubs, before joining AaB in 2017 at the age of 12.
[3] Possessing a physique suited for the goalkeeping position, Sander impressed in various youth teams and attracted interest from some of Europe's major clubs.
[7] On 20 July 2023, after AaB suffered relegation to the second division, Sander joined Copenhagen, on a deal until June 2028.
[8] He made his competitive debut for the club on 18 August, replacing an injured Kamil Grabara as starter in goal, keeping a clean sheet in a 2–0 victory against Hvidovre.
[11] In search of more playing time, on February 3, 2025, on transfer deadline day, it was confirmed that Sander moved to Danish 1st Division club Hvidovre IF on a loan deal for the rest of the season.