That's a felony of the second degree in Texas. If someone gets sick from it, it becomes a felony of the first degree. The other suggestions wouldn't result in litigation, whereas this one could/would.
All right, then. Don’t spit or hawk a lung oyster in their entree. Burn it. Oversalt it. Add some Tabasco to their ice cream. Oops! Accomplishes the same thing by “accident” and is not actionable.
Or don’t even. be that overt. Just make the food so lousy that even if they eat it, you’ll have proved your point. And if they don’t eat it, you’ve also won.