Peel and roughly chop the guava, about 2 cups / 300 g, discarding any tough core pieces.
If you want a smooth drink, blend the guava alone for about 20 seconds, then push it through a fine-mesh sieve into a bowl to remove the seeds. Skip this step if you don't mind texture.
Add the strained (or chopped) guava to the blender along with the coconut water, lime juice, lime zest, and frozen banana.
Blend on high for 45 to 60 seconds until completely smooth and no chunks remain.
Taste the mixture. If the guava was tart, add the honey and blend for 5 more seconds to combine.
Add the ice cubes and blend again for 20 to 30 seconds until the smoothie turns pale pink and frosty.
Pour into two glasses.
Garnish with fresh mint leaves and serve right away while it's cold.