minecraft-assets/data/minecraft/loot_table/dispensers/trial_chambers/water.json

{
  "type": "minecraft:chest",
  "pools": [
    {
      "bonus_rolls": 0.0,
      "entries": [
        {
          "type": "minecraft:item",
          "functions": [
            {
              "add": false,
              "count": 1.0,
              "function": "minecraft:set_count"
            }
          ],
          "name": "minecraft:water_bucket"
        }
      ],
      "rolls": 1.0
    }
  ],
  "random_sequence": "minecraft:dispensers/trial_chambers/water"
}