Tone down the bitterness of grapefruit juice and sweeten it up by combining it with carrot or beet juice, both of which are naturally sweet. You can buy carrot juice at the grocery store but you might have to do a little sleuthing to find beet juice. You can make your own beet or carrot juices, too.

Some varieties of grapefruit are sweeter than others. For example, pink and red grapefruit taste sweeter than white grapefruit. The color is from the flesh rather than the skin. Pink grapefruits are mostly yellow on the outside, blushed with pink. Red grapefruit are blushed with a deeper shade of pink on the skin. White grapefruits are yellow.

Sweet berries, such as strawberries and blueberries, sweeten grapefruit juice. Puree the berries or muddle them in the bottom of the glass with a spoon and then add the grapefruit juice. An alternative is to add a bit of sweet fruit nectar such as apricot or peach. Apple juice won't change the color of the grapefruit juice much and neither will white grape juice. Any fruit you add will change the flavor of the juice.

Artificial sweeteners are manufactured products. Sucralose is 600 times sweeter than sugar, and it is used for both drinks and baking. Aspartame is 200 times sweeter but is only used for beverages. Saccharin varies from 200 times sweeter to 700 times, and is appropriate for both beverages and baking. The different sweeteners have different tastes and aftertastes. Some artificial sweeteners are blended with natural sweeteners for a more appealing taste.

The quickest way to improve the taste of grapefruit juice is to add a sweetener such as white sugar. It doesn't change the flavor or the color of grapefruit juice. Other natural sweeteners, such as brown sugar, honey or maple syrup, change both the flavor and the color. Stevia is produced from the leaves of the stevia plant. It has a bitter aftertaste that is removed through processing the commercial product. It is 200 times sweeter than white sugar.