Salt water is NOT a safe homemade emetic.
If mixed correctly, it is actually recommended by doctors (including the Mayo Clinic) to settle the stomach and prevent vomiting. If mixed incorrectly, it is toxic.
It might induce vomiting, but it will cause weakness, cramping, and extreme thirst. It can also restrict breathing and cause kidney damage.
Poisoning oneself to combat a suspected drugging is not going to improve the situation.