Lookman played for 90 minutes as Atalanta made it two wins from two group games.
The former Everton and Leicester player created three chances in the course of the game.
Giorgio Scalvini opened the scoring in the 33rd minute before Matteo Ruggeri made it 2-0 on 43 minutes.
Victor Gyokeres pulled a goal back for Sporting from the penalty spot in the 76th minute.
Atalanta have six points and top the group while Sporting Lisbon are second on three points.
In Group C, Aris Limassol defeated Rangers 2-1 with Cyriel Dessers featuring for 90 minutes.
Leon Balogun was not in the Rangers squad for their second group game.
Rangers have three points and are third in the group after two games played.
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