Is there an optimum amount of baking soda and vinegar to put in a plastic soda bottle rocket? How would you figure that out?

Add 1 tsp. of vinegar to the canister at a time, filling it almost to the top. You need to add as much vinegar to the canister as possible without the vinegar and the baking soda coming into contact when you later snap the lid onto the canister. Depending on the exact canister, this may be around 5 tsp.