Kiki beat me to it! No need to give electrolytes on a daily or even regular basis. It can be detrimental, throw off the electrolyte balance in their systems, and may even be hard on their kidneys. Simply give them good fresh plain water, unless they are overheated, stressed, or showing signs of heat stroke.
As for keeping an antibiotic in your "emergency kit" I would not bother. #1: IIRC, you now need a vet Rx. for an abx. #2: They have a short shelf life, and may very well expire before you ever have the need. I've been raising birds (this time around) for 4.5 years, and have never needed any type of antibiotic. #3: You need a specific antibiotic for a specific microbe. It's like being blindfolded and tossing a dart at a dart board, hoping that your Antibiotic dart will hit the bulls eye to target the "Microbe" that is causing the illness in your flock. We all know that blindly treating human or animal with antibiotics has gotten us to the place we are at today: microbes that are resistant to current antibiotics. #4: Best to combat the mentality of reaching for the medication. Instead, develop the mentality of providing good animal husbandry so you will most likely never need an antibiotic in the first place. Build your flock's immune system: Deep litter, fermented feed, good nutrition. Take care of your land: rotation of flock through a paddock system, never overstocking your available space, deep litter. Bare soil is soil that is likely to harbor pathogens of all kinds. Cull weak or ill birds so they will not be a disease vector for the rest of your flock.
Am I saying to NEVER use an antibiotic? No. that is an individual decision. What I am saying is that you should never use an antibiotic unless you are treating a specific injury, or a specific diagnoised disease, and then only use the antibiotic as directed by a vet.