In the 16th minute, referee Cuadra Fernandez activated the anti-racism protocol after Sannadi was targeted with insults, which were reported by his teammate Inaki Williams.
The game was paused for three minutes while an announcement was made over the public address system, urging spectators to cease their offensive chants. The referee issued a warning that any further disruptions would result in another stoppage.
"This kind of behavior should never occur. This is not the first time it has happened here. The referee handled the situation excellently. We must hold those responsible accountable," stated Williams.
After play resumed, Espanyol took the lead in the 62nd minute with a goal from Roberto Fernandez, but Oihan Sancet, who netted a hat-trick in Bilbao's previous win over Girona, equalized just 15 minutes later.
For both teams, the outcome was far from ideal.
On Saturday, both Real Madrid, the league leaders, and second-place Atletico Madrid were also held to draws.
Bilbao's draw leaves them in fourth place, three points behind Barcelona, who will play Rayo Vallecano on Monday, and six points adrift of Real Madrid.
Espanyol, while disappointed by the dropped points, managed to climb out of the relegation zone. They now sit 15th with 24 points, just one point ahead of Valencia, who occupy 18th place, the first relegation spot.