Citrus juice
Speaking of premade things, why would you buy premade citrus juice on a regular basis? If you do not have a problem with your wrist, squeezing the juice out of lemons, limes, oranges, and even grapefruits is not going to be that hard, and you will be able to make yourself a great drink in a matter of minutes!
The problems with premade juices come down to one thing in particular: presqueezed juice is going to start changing in taste the longer it has been sitting, be it on the counter or in the fridge, and you do not want a funky-flavored juice.
And if you end up buying the premade stuff from the store, you do not know how long it has been there. Sure, there are a few freshly squeezed options, but not always. The ones that do not mention when they were squeezed are bound to have a ton of preservatives, and they could even have sulfites. Check your labels carefully!