The Liquipack mod adds a backpack to Minecraft that holds either water or lava right on your back. It comes in 3 different tiers from small to large that contain 10000mb, 20000mb, or 30000mb of liquid. It’s a great way to carry a great amount of liquid without taking up a significant amount of inventory space.
There are a few ways to add liquid to the pack. You can hit the ‘L’ key to open up the pack’s GUI to manually add water or lava via bucket. Just select which tank you want and load a full bucket in the left slot to add liquid. You can add an empty bucket in the same slot to remove liquid as well.
Another option is to create the Liquipack bucket. It will either empty or fill your tank(s) depending on how you set it. Shift+right-click while holding the bucket and you can select either to drain or fill and which tank to do so from. Then you can right-click the bucket where you want to add water/lava or on whatever liquid you want added to the selected tank.