Wiktionary
n. A three-dimensional puzzle in the form of a drinking vessel made of three or more cups or jugs all linked together by holes and tubes. The challenge is to drink from the vessel without spilling.
Wikipedia
A fuddling cup is a three-dimensional puzzle in the form of a drinking vessel, made of three or more cups or jugs all linked together by holes and tubes. The challenge of the puzzle is to drink from the vessel in such a way that the beverage does not spill. To do this successfully, the cups must be drunk from in a specific order.
Usage examples of "fuddling cup".
The jollity increased when someone else brought out a three-merry-boys fuddling cup, a trio of mugs whose bodies were joined and whose handles were interlinked so that they had to be emptied simultaneously to prevent spillage.