The Spaniard won 6-3 3-6 10-7 in the opening match of the tournament at the Steffi Graff Stadium.
The Bett1 Aces is a grass exhibition event featuring ATP and WTA players and played in front of a limited number of fans.
Rain halts Tsitsipas charge as he leads Djokovic overnight
Highlights: Roberto Bautista Agut beats Jan-Lennard Struff in Berlin
After dropping serve in the opening game, Bautista Agut battled back to take the first set against Struff.
The German took the second set with a break in the sixth game, but Bautista Agut edged the match tiebreak to win the contest.
'Brilliant' - Roberto Bautista Agut produces sublime winner in Berlin
Julia Goerges retired from her match against Anastasija Sevastova due to injury, trailing 6-4 4-3.
Former world No 2 Tommy Haas plays Jannik Sinner on Monday while Petra Kvitova faces Andrea Petkovic from around 5pm.
Heavy rain stops play in Rome with Tsitsipas leading Djokovic
Arm injury forces Barty out of Italian Open