Hi, Denise !
Let me ask you this, how does your throat feel after drinking regular orange or grapefruit juice ? If citric acid is bothering your throat, you should see the same problem if you drink orange juice. what happens if you eat an orange, lime, lemon or grapefruit ? Does eating citrus fruit bother your throat ? If not, it might not be the citric acid per se. It could be the artificial chemicals in those flavorings you use.
Instead of using Crystal light, why not try a squeeze of fresh lemon or lime ? that would be a healthier option than those mixes.
When I was starting to increase my intake of water, I was drinking sparkling waters like Poland Springs, Adirondak, Perrier, Whole Foods mineral waters, etc... If you need a fizzy fix, sparkling waters are great. love them.