Give the flamethrower a reload animation, here’s how it will work.

The animation starts by unscrewing the red bottle, and then filling it with a bottle of kerosene from the players inventory, then the red bottle is reattached and there!

If the player does not have any bottles of kerosene then the animation won’t start, if the player does have a bottle then it will use the bottle with the least percentage, if the player has more than one bottle that is at 100% it will reload using a random bottle.

The amount of percentage the flamethrower gains scales with the amount of percentage the bottle has so for example:

If the player has a bottle of kerosene that is at 30% and the flamethrower is at 60% then it will keep reloading until the bottle is empty which would leave the flamethrower at 90%, after it’s empty the empty bottle gets automatically ejected from the players inventory (show an animation of the player throwing it out), if the flamethrower is at 90% and the player has a bottle that is at 60% then the player would continue reloading the flamethrower until it is at 100% and then afterwards the player would put the bottle back in their inventory.

By doing this, the player will be able to carry bottles of kerosene in the back of their inventory, without needing to place them in the hot bar, so all you need to do is just make sure you have bottles of kerosene in your inventory and reloading the flamethrower would be easy!