Well, for one thing, what you did is not an experiment. What you did was to create a model. Modeling is something scientists actually do, but not all scientists do experiments, and few geologists who study volcanoes do them. In fact, the scientific method is a myth. Scientists use a variety of methods and few if any follow those steps. Sounds like your teacher or your school curriculum need to be updated. That myth of the scientific method is 100 years old and took John Dewey's idea out of context.
1 tbsp baking soda
1/4 cup vinegar
60 ml water
little drops of detergent
orange food coloring
piece of tissue.
Place the water, soap, food coloring and vinegar in the drink bottle. Wrap the baking soda in the tissue and drop into the bottle. The volcano model will then erupt.
Pour the food color, soap vinegar and water in the bottle. Before you drop the baking soda, wrap it in a tissue then the volcano model will ooze with lava. To be more realistic you can cover the bottle homemade play dough. The chemical reaction by the way is: NaHCO3 + CH3COOH → Na+ + H2O + CO2 + CH3COO where the Carbon dioxide is released that creates the fizz.
You could buy all the stuff on that other persons list or................ you could make and decorate a cone that with fit over a 2 liter of diet coke. Then drop a few mentos into the open 2 liter and boom. Easy as pie. That reminds me got to go make a pie.