Half of the world's fruit production goes to grapes. Most grapes are used for production of foods marketed as being without added sugar. For this use, the juice is treated to remove the flavor and pretty much everything else except for the sugar and water.
Though not always, flavor can usually be guessed by color and size. Very large grapes tend to have a weak flavor. Green grapes also tend to have a weak flavor. Red grapes tend to have a fairly full flavor. Purple grapes tend to have the flavor of red grapes plus a sort of harsh bitter taste. Grapes with seeds tend to have better flavor than grapes without seeds.
Grapes are not normally cooked, except to demonstrate odd properties of a microwave oven. Cut the grape nearly in half, leaving a very thin connection. Place the grape in the microwave oven with the cut sides up. Microwave the grape.