You seem to have received a standard coffee vending machine, the only noticeable difference being an entry touchpad with buttons corresponding to an English QWERTY keyboard. Upon depositing fifty cents US currency into the coin slot, the user is prompted to enter the name of any liquid using the touchpad. Upon doing so, the machine places a standard 12-ounce paper drinking cup before the liquid indicated is poured. Requests that have succeeded includes common beverages (like water, coffee, beer, and soda), non-consumable liquids (examples include sulfuric acid, wiper fluid, and motor oil), substances that do not usually exist in liquid state (such as nitrogen, iron and glass) to even the esoteric and abstract like "a cup of pertinent medical knowledge" or "a cup of music".
To note, their do seem to be limitations inherent to this machine. For instance, after extensive experimentation, it was determine that after approximately fifty uses, the machine would not respond to further requests. After a period of approximately 90 minutes, the machine seemed to have restocked itself. Furthermore, SCP-294 will not provide any requests for solid substances (like "a cup of diamond") and it is theorized that SCP-294 has a limited range of collection, ie, it cannot reach into alternate universes/dimensions. Their might be more, so be on guard with your choices, especially if you input something like a "cup of godhood".