Goblets are fancy vessels that can be placed on most solid surfaces. This is one of the items which can hold many different kinds of drinks. To fill them, right click on a barrel of the drink that you want to fill the goblet with, and then either place it down on a solid block, or drink it by holding down right click. There are 4 varieties: Wooden (which are called cups instead of goblets), copper, silver and golden.
Right clicking on a placed goblet will make you drink it instantly. Also, you can right-click an empty vessel with a full one in your hand, or vice versa to transport the fluids to and from each other.
One way to obtain goblets is by looting. The more valuable goblets (gold and silver) are most often found in Dorwinion (most often in breweries). They are also frequently found in Gondor structures (mostly taverns) and in Lindon structures (especially in halls).
If you don't like to steal goblets from buildings, then you can craft your own, using the following patterns on a regular crafting table. You may use either wooden planks, copper ingots, silver ingots, or gold ingots to make goblets, which will result in a wooden, copper, silver, or golden goblet, respectively:
The anglo-saxon calc-rune ᛣ or ᛤ (= letter K or KK) means "chalice" or "goblet". Tolkien used those ᚱᚢᚾᛖᛋ for some texts in the initial drafts of "The Lord of the Rings", later on, he replaced them by cirth runes. Sorry, no quote (not included in the Old English rune poem).