Fred has a large piece of sugar that is not dissolving in his drink. how could he get the sugar chunk to dissolve faster?

He can do more than one thing.  Each of them will increase
the rate at which the lump dissolves.

-- The easiest action, and the one with the quickest effect,
is to crush the chunk into normal, un-chunked sugar, so that
the liquid can reach much more surface area of sugar.

Other possibilities:

-- Stir the drink constantly until the sugar is completely dissolved.

-- Heat the drink.