Put the sour cream into the bowl and gently mix it until soft. Add the whipped topping and gently mix it into the sour cream until you have a smooth base for your ambrosia.
Drain the liquid out of the mandarin oranges and the cherries; then add the fruit into the bowl. Mix in the bananas and coconut flakes.
Make sure the marshmallows are room temperature—or even slightly warm—and add them to the bowl with the other ingredients. Stir all the ingredients gently until the marshmallows settle into the mixture easily.
Add sugar to taste. It’s okay to add more than one tablespoon but don’t overdo it!
Carefully add the ambrosia into the blender and mix for 1 minute on medium speed. Slowly pour the pear or guava nectar into the blender and mix for 1 to 2 minutes, until you are happy with the consistency, which should be smooth and not too thick.
Serve cold in a tall glass with a cherry (with stem) and an umbrella. Enjoy!