Rehydration solution made at home

A.K.A. Hacking pedialyte.
a) contents:

Water, Dextrose. Less than 2% of the Following: Potassium Citrate, Sodium Chloride, Sodium Citrate, Citric Acid, and Zinc Gluconate.

PEDIALYTE PROVIDES (PER LITER): Sodium, mEq: 45; Potassium, mEq: 20; Chloride, mEq: 35; Zinc, mg: 7.8; Dextrose, g: 25; Calories: 100

Someone please tell me what the hell is mEq - because I've worked in molecular lab for over ten years and never herd of such measurement.

Looked it up:
milliequivalent (mEq)

[-ikwiv′ələnt]

Etymology: L, mille + aequus, equal, valere, to be strong

1 the number of grams of solute dissolved in 1 ml of a normal (1 N) solution.

2 one thousandth (10^-3) of a gram equivalent.

Mosby's Medical Dictionary, 8th edition. © 2009, Elsevier.

all I have to say is - WTF, never mind I got it... millimolar

b) what wiki has to say:

".... electrolyte absorption while a child is sick and contains the quantity and ratio of the sugars glucose and fructose, and electrolytes recommended by the American Academy of Pediatrics (AAP). This makes it very low in sugar compared to most sports drinks (100 calories/liter vs. Gatorade's ~200) and higher in both sodium (1,035 mg/L vs. Gatorade's 465) and potassium (780 mg/L vs. Gatorade's 127). Sucrose is not used in Pedialyte because of the risk of making diarrhea worse by drawing water into the intestine and increasing the risk of dehydration."

mg/L is something I do understand.. it's milligrams per liter - just in case...
and I have no idea where or how they got their numbers...

c) science literature:

http://www.ncbi.nlm.nih.gov/books/NBK63837/#_ncbi_dlg_citbx_NBK63837

"What is the most effective composition of ORS solution?

ORS solution has been manufactured using a range of constituents in differing concentrations. Various organic solutes have been included such as glucose, starch and amino acids. Sodium chloride has been used in varying concentrations. Other non-essential constituents, including potassium, bicarbonate and acetate are often included. Much research has been carried out to evaluate the effectiveness and safety of these various solutions. Two key areas of research have focused on the optimal sodium/osmolar concentration in ORS solution and on the relative efficacies of glucose versus rice starch as the organic constituent in ORS solution.

The composition of the original WHO ORS solution (glucose 111, sodium 90, potassium 20, chloride 80 and bicarbonate 30, all in mmol/l) was selected to allow for use of a single solution that would effectively treat dehydration secondary to diarrhoea caused by various infectious agents and resulting in varying degrees of electrolyte loss.19 However, in developed countries, viral gastroenteritis is common and is associated with less severe salt losses, and so there was concern that the sodium content of the original WHO ORS solution might be excessive.88 From the 1970s, efforts focused on improving the efficacy of ORS solution by altering its composition. It was found that solutions with higher concentrations of co-transporters (such as sugars) and higher osmolarity decreased rather than increased intestinal sodium and water absorption. Additionally, hypernatraemia was reported with their use. The current formulation WHO ORS solution adopted in 2002 (glucose 75, sodium 75, potassium 20, chloride 65 and citrate 10, all in mmol/l) preserves the 1 : 1 molar ratio of sodium to glucose that is critical for efficient co-transport of sodium. It has a reduced osmolar load (245 mOsm/l) compared with the original formulation (311 mOsm/l). It also has a longer pre-mixed shelf life owing to its citrate content."

http://www.ncbi.nlm.nih.gov/books/NBK63837/table/ch5.t1/?report=objectonly

Hmmm... Nothing on Zinc and 7.8mg/L sounds a bit high... or it just could be me.
Lets look it up...
http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5216a1.htm
"

Supplemental Zinc Therapy

Multiple reports have linked diarrhea and abnormal zinc status (77), including increased stool zinc loss, negative zinc balance (78), and reduced tissue levels of zinc (79). Although severe zinc deficiency (e.g., acrodermatitis enteropathica) is associated with diarrhea, milder deficiencies of zinc might play a role in childhood diarrhea, and zinc supplementation might be of benefit either for improved outcomes in acute or chronic diarrhea or as prophylaxis against diarrheal disease. Reduced duration of acute diarrhea after zinc supplementation among patients with low zinc concentrations in rectal biopsies has been demonstrated (79). In Bangladesh, zinc supplements also improved markers of intestinal permeability among children with diarrhea (80). In India, zinc supplementation was associated with a decrease in both the mean number of watery stools per day and the number of days with watery diarrhea (81). Prophylactic zinc supplementation in India has been associated with a substantially reduced incidence of severe and prolonged diarrhea, two key determinants of malnutrition and diarrhea-related mortality (82). In Nepal, this effect was independent of concomitant vitamin A administration, with limited side effects apart from a slight increase in emesis (83). In Peru, zinc administration was associated with a reduction in duration of persistent diarrhea (84). In two different pooled analyses of randomized controlled trials in developing countries (85,86), zinc supplementation was beneficial for treating children with acute and persistent diarrhea and as a prophylactic supplement for decreasing the incidence of diarrheal disease and pneumonia. Among infants and young children who received supplemental zinc for 5 or 7 days/week for 12--54 weeks, the pooled odds ratio (OR) for diarrhea incidence was 0.82 (95% confidence interval [CIs] = 0.72--0.93), and the OR for pneumonia incidence was 0.59 (95% CI = 0.41--0.83). The efficacy and safety of a zinc-fortified (40 mg/L) ORS among 1,219 children with acute diarrhea was evaluated (87). Compared with zinc syrup administered at a dose of 15--30 mg/day, zinc-fortified ORS did not increase the plasma zinc concentration. However, clinical outcomes among the zinc-fortified ORS group were modestly improved, compared with those for the control group, who received standard ORS only. In that study, the total number of stools was lower among the zinc-ORS group (relative risk: 0.83; 95% CI = 0.71--0.96), compared with the total number for the control group. No substantial effect on duration of diarrhea or risk for prolonged diarrhea was noted.

Thus, a number of trials have supported zinc supplementation as an effective agent in treating and preventing diarrheal disease. Further research is needed to identify the mechanism of action of zinc and to determine its optimal delivery to the neediest populations. The role of zinc supplements in developed countries needs further evaluation."

d) shopping for ingredients:

Zinc Gluconate
Molecular formula C12H22O14Zn
Molar mass 455.685 g/mol

Sodium Citrate (trisodium citrate)
Molecular formula Na3C6H5O7
Molar mass 258.06 g/mol (anhydrous), 294.10 g/mol (dihydrate)

Potassium Citrate
Molecular formula C6H5K3O7
Molar mass 306.395 g/mol

Sodium Chloride
Molecular formula NaCl

Mollar mass 58.44 g/mol

Citric Acid
Molecular formula C6H8O7
Molar mass 192.124 g/mol (anhydrous), 210.14 g/mol (monohydrate)

Glucose 

Molecular formula C6H12O6
Molar mass 180.16 g/mol

I say just go for the cheep stuff...

Modernist Pantry will have almost everything you need.

After much deliberation I've decided to go for the WHO ORS solution, addition of Zinc Gluconate is optional. 

So lets make it:

glucose 75mmol/L - 13.512 grams

sodium 75mmol/L in NaCl - 3.7986 grams in Na3C6H5O7 - 2.5806 grams

potassium 20mmol/L in C6H5K3O7 - 6.1279 grams

chloride 65mmol/L already there in the form of NaCl

citrate 10mmol/l in C6H8O7 - 1.9212 grams

zinc (optional) since no molar concentration is provided anywhere you can use 7.8mg per L as described in Pedialyte composition.  You can get some here.

Put all the dry ingredients into a volumetric cilinder and water to 1 liter.

If you are wondering is I actually did the number crunching... no, Molarity Calculator did the job:-)

PS Please correct me if I'm wrong.

PPS I'll make a neat little table for you later.