We will try corn syrup and water in this experiment. We will hope the water has enough minerals. This mixture has very little nitrogen and will don't know if the yeast will be able to grow, if it does not grow we will try to find a nitrogen source to add. It tapwater does not have enough minerals, we could try water from a mud puddle or soil water made by mixing soil with water and using the clear supernatant water after the mud has settled. If the yeast does not grow we could try meat broth, or other source of amino acids.
Corn syrup is mostly glucose which is a sugar most microbes can use.
Recalling that a liter is 1000 ml or 1000 cubic centimeters, we will add 10 cc of corn syrup to a liter of water. Your ruler is marked in centimeters. So we want to add a slug of cornsyrup about 1 cm x 1 cm x 10 cm long. You can estimate this volume easily and you need not be exact for this first experiment. Read the label on your syrup.