Wing-back Hakimi, signed from Inter after he helped the Nerazzurri win Serie A last season, was handed his first, unofficial start for PSG in the training ground match on Thursday (AEST).
The former Real Madrid youngster teed up PSG's second goal, squaring for Ismael Gharbi to sweep home from the centre of the area.
Mauricio Pochettino's team had gone ahead in the 12th minute against their second-tier opposition, with Icardi on hand to head home after the Le Mans goalkeeper had parried Julian Draxler's cross into his path.
Icardi scored 20 goals in his first season at PSG, on loan from Inter, but failed to replicate that level of performance last term, netting just 13 times.
Bandiougou Fadiga replaced Icardi at half-time, and his 87th-minute strike made it 3-0 before fellow substitute Xavi Simons rounded off the scoring.