Add prickly pear pulp, sugar, water and lime juice to a small sauce pan. Bring the mixture to a low boil, stirring to ensure all of the sugar is dissolved, then lower the heat to a simmer and let cook for 15 minutes. Transfer the mixture to a blender, push through a fine sieve and let cool.
To assemble the drink, add prickly pear syrup, tequila alternative and lime juice to a shaker with ice. Shake to combine, then divide this mixture between two glasses over ice. Top off with tonic water and enjoy.
Nutrition information is automatically calculated, so should only be used as an approximation.