Step 1: Acquire an expensive consumable item, such as a Xesperra's Scroll of Madness


Step 2: With Keyboard controls, hover over the item in your inventory and press an actionbar button to assign it to that slot


Step 3: With Mouse controls, click and drag the item out of the hotbar into the game world


When you release the mouse button you will get +1 of whatever consumable item you used.

Repeat for infinite whatevers.