Happy New Year!
So, in keeping with your New Year's Resolutions, maybe you've decided to switch to diet. With homemade, it's easier than you might think.
One of my favorite commercial sodas of all time is Squirt. Its zesty citrus flavor is hard to beat. (Maybe you've noticed, but I do love citrus!) Its skinnier doppelganger, Fresca, is not so much my favorite, but mainly because I'm not a big fan of alternative sweeteners. They just have a bitter flavor to me. And Fresca's image was kind of, well, grandma-ish.
However, a few years ago, Fresca revamped their brand. They changed their packaging, logo, and added some extra flavors. Nicely done, Coca-Cola, nicely done. Their flavor combinations pulled the diet grapefruit out of the "blah".
When I decided to do a diet recipe, Fresca just seemed a nice fit, but I also decided to pull it out of the "blah" with some cherry flavor. Admittedly, you can do any of my recipes diet, just swap out the sugar with equivalent amounts of sucralose(Splenda) or stevia extract, or whatever alternative sweetener you prefer. Avoid heating aspartame (Nutrisweet or Equal) as it turns bitter, but sucralose is alright to heat. You don't need to, but it does dissolve quicker.
2 cups Splenda
1tsp citric acid (optional, but worth procuring)
1 tsp cherry or almond flavoring
1 gallon (4L) carbonated water or club soda
First, juice your grapefruit. If you section and score it, it juices easier.
Next, zest your grapefruit. I've found that you don't have to be as careful with zesting grapefruits as you do with other citrus, it's just as bitter with or without the white pith.
Steep your zest in a cup or two of hot water for about 15-20 minutes. I like to keep mine covered because I believe it retains more flavor that way, though I have no hard proof of that. Strain to remove the zest and add your sweetener to infused water, then add your grapefruit juice. Once cooled, add the cherry flavoring (and a few drops red food coloring if you wish, helps people recognize the cherry flavor a bit better). Top up to 1 gallon with carbonated water and that's it!
Some notes on alternative sweeteners:
I used the sucralose from the grocery store that's intended to be a cup for cup replacement for sugar intended to making converting recipes easier. This is actually sucralose spray dried onto a maltodextrin carrier, so it's not pure sucralose. Don't be confused by the fact that pure sucralose is actually many times sweeter than sugar and can't be substituted in the same way. If you happen to get your hands on some pure sucralose, keep in mind that you will in fact use much less of it (a few grams, if that).
Ace K or Acesulfame Potassium is another that is similar to sucralose. You may find a source online, but otherwise it's difficult to find. This is something that's best used with other sweeteners, like a 50/50 blend with sucralose. As I understand it they have a symbiotic relationship of sorts, so you end up using less for the same effect.
As noted above, aspartame should not be heated. It will break down and become bitter. I made that mistake once in making some barbecue sauce with diet coke, not a good plan. If you buy Equal in the store, it should have a sugar equivalent listed somewhere in terms of teaspoons of sugar. (48 teaspoons are in a cup).
I have never used stevia extract, so I can't really offer any advice on that one. I've heard mixed reviews on that one. If you're afraid of anything "artificial", stevia is probably the easiest route for you to take right now other than just cutting out sugar and not trying to make up for the lost sweetness, which in my mind is the most noble, and probably most effective. You might also look into monk fruit or even miracle berry(syssepalum ducificum) if you don't mind digging for sources.