I don't want to say why but I need to make myself as sick as possible overnight
Do you have any food intolerances, personally if I drink a glass of milk I vomit .
Making you sick with rotten food is not a good idea.
You might try some medicines that make you vomit. Emetics o large dose activated charcoal can induce vomiting. If you want to go full way you could add a laxative so you get diarrhea too. :)
I once faked vomiting by making a glass of water with 1-2 tablespoons of mustard .I mixed untill I it got the texture and yellowish color of vomit and added small bits of food in it. So I took it to bathroom made some noises threw half of it in toilet to make a mess, called my mom and kept the other half in mouth and throw it up just the moment she came in. It worked;) I was a child back then.