1. Have 2 beverage cans in your inventory
2. Drink one of the cans (inventory screen -> drink)
3. As the drinking sound is playing, grab the other soda and hover it over the soda can you are currently drinking from. Don't release the mouse.
4. When the drinking process is finished, the can remains in the inventory.
5. Now you can release your mouse-held soda into any slot.
6. The original can you drank from now has unlimited uses.