Blend Rice Base: Add the uncooked rice and water to a blender. Blend for 30 to 60 seconds, until the water looks cloudy and the rice is broken into small pieces.
Chill Rice Mixture: Pour the rice mixture into a container or keep it in the blender jar. Let it chill for 15 to 20 minutes while you prepare the tacos.
Make Lime Dressing: In a large bowl, zest the lime, then cut it and squeeze in the juice. Add the chopped cilantro and mayonnaise, then stir until smooth.
Toss Slaw: Add the coleslaw mix to the bowl. Toss until the cabbage is evenly coated, then set aside.
Coat Shrimp: Put the shrimp in a medium bowl and add the spicy ranch dressing. Stir until all of the shrimp are fully coated.
Bread Shrimp: Pour the fish fry mix into a shallow dish. Dredge each shrimp in the mix until fully covered.
Heat Oil: Add the vegetable oil to a skillet and warm it over medium heat for about 2 minutes, until shimmering.
Fry Shrimp: Cook the breaded shrimp in batches so the pan does not get crowded. Fry for 2 to 3 minutes per side, until golden brown and cooked through, then transfer to a plate.
Warm Tortillas: Heat the flour tortillas in a dry skillet over medium-low heat for about 15 to 30 seconds per side, just until warm and flexible.
Build Tacos: Lay out the warm tortillas and add a few avocado slices to each one. Top with the crispy shrimp, then spoon the slaw over the top.
Finish Sweet Rice Drink: Strain the chilled rice mixture through a fine-mesh strainer into a pitcher. Stir in the sweetened condensed milk, vanilla extract, and most of the cinnamon, saving a small pinch for topping.
Serve: Pour the sweet rice drink into glasses and sprinkle the reserved cinnamon on top. Serve right away with the tacos.