What I want to know is how much the sparkling power boosts the odds of getting a shiny since I have the ingredients and recipes to make lvl 3 sandwiches.
Sparkling Power increases your Shiny Odds by four, to 1/1024. It also stacks with Shiny Charm and Outbreak defeats. Sparkling Power and 30-59 Outbreak defeats increase odds to 1/819, while 60+ defeats will earn you odds of 1/683. Sparkling Power with Shiny Charm also increases Shiny odds to 1/683.
Combining all three, Sparkling Power with Shiny Charm and 30-59 Outbreak defeats will give you odds of 1/585, and 60+ defeats will give you max odds of 1/512.
Other methods and odds for shiny hunts.