In a large glass jar, combine the alcohol, bitter orange peel, gentian root, wormwood, and cinchona bark. Seal the jar tightly and let it infuse for 10 to 14 days, shaking it occasionally.
After the infusion period, strain the mixture through a fine-mesh sieve or cheesecloth to remove the botanicals. Discard the solids.
In a saucepan, bring the water to a boil. Add the sugar and stir until completely dissolved. Remove from heat and let the syrup cool.
Combine the infused alcohol with the sugar syrup in a large container. Stir well to ensure proper mixing.
Add orange zest to the mixture for an extra citrus note. If desired, you can add a few drops of red food coloring to achieve the characteristic vibrant red color of Campari.
Transfer the homemade Campari to a bottle or airtight container, and let it rest for at least a week to allow the flavors to meld together.