Will a 4oz bottle of Robitussin DM make me puke my guts out?

I think you're good, since you're a big guy. If you feel nauseous you could eat. Wikipedia says it's best to take guaifenesin with food. This drug is dissociative, so don't do it anywhere unsafe. My friend took the pills on a rooftop and ran off of it because she thought she could fly! I don't think you're that stupid, especially if you're asking questions and researching.