According to Tori the waiters there spit in their food because Trina never tips the waiters. The whole conversation was:
Trina: Did you know in Italy you're not supposed to tip your waiters? That's why I never tip at the Olive Bargain. Makes the meal more authentic.
Tori: And that's why I never go to the Olive Bargain with you. I just know they're spitting in our food.
In a deleted scene of Stage Fighting, Robbie says to Rex, "Well, I guess it's dinner for two at the Olive Garden," and Rex says, "Oh NO! Not the Olive Garden! Please!", but this was before the writers changed the name to "Olive Bargain."