Pumpkin/assets/datapack/data/minecraft/recipe/brewing/potion_water_gunpowder.json

{
  "type": "minecraft:brewing",
  "input": {
    "item": "minecraft:potion",
    "potion_contents": {
      "potions": "minecraft:water"
    }
  },
  "output": {
    "components": {
      "minecraft:potion_contents": {
        "potion": "minecraft:water"
      }
    },
    "id": "minecraft:splash_potion"
  },
  "reagent": {
    "item": "minecraft:gunpowder"
  }
}