Sweeney played five seasons for the Boston College Eagles, redshirting his freshman season. As a redshirt junior, he led the team with 36 receptions, 512 receiving yards, and four touchdown receptions and was named third-team All-Atlantic Coast Conference (ACC).[3] He capped off the season with seven catches for 137 yards and a touchdown against Iowa in the 2017 Pinstripe Bowl. In his final season with the Eagles, Sweeney had 32 catches for 348 yards and three touchdowns and was named first-team All-ACC.[4] Sweeney finished his collegiate career with 99 receptions for 1,281 yards and 10 touchdowns in 38 career games.[5]
Sweeney was drafted by the Buffalo Bills in the seventh round (228th overall) of the 2019 NFL draft.[8] He signed a rookie contract with the team on May 9, 2019.[9]
Sweeney made his NFL debut in the on September 8, 2019, in the Bills season opener, catching two passes for 35 yards in a 17–16 win over the New York Jets.[10] Sweeney caught eight passes for 114 yards in six games played as a rookie.[11]
Sweeney was placed on the active/physically unable to perform list (PUP) by the Bills due to a foot injury on July 28, 2020.[12] He was placed on the reserve/PUP list to start the season on September 5, 2020.[13] He was moved to the reserve/COVID-19 list by the team on October 24, 2020,[14] and was activated back to the PUP list on November 11.[15] However, he developed myocarditis as a result of the virus and was ruled out for the rest of the season.[16] He was placed back on the reserve/COVID-19 list on November 23, 2020.[17] In April 2021, Bills general manager Brandon Beane announced that Sweeney should be ready for the 2021 season.[18] Sweeney returned to the field in June 2021, when it was revelated that at one point in time, it was unknown if he'd be able to play again.[19]
On October 18, 2021, Sweeney caught his first career touchdown in a loss to the Tennessee Titans.[20]
New York Giants
On March 23, 2023, Sweeney signed with the New York Giants.[21] On August 23, Sweeney collapsed on the practice field as the result of a 'medical event.' He was placed on reserve/non-football injury list six days later, and did not play for the Giants in 2023.[22] Sweeney was released by New York on November 28.[23]
Chicago Bears
On May 13, 2024, Sweeney signed with the Chicago Bears.[24] He was released on August 24, and re-signed to the practice squad on October 9.[25]