Pedialyte. Although made for children, I've found it very effective in adults.

Electrolytes is the term used to refer to ions present both inside and outside cells that help to regulate various processes for the cells to function correctly. For example, sodium ions are used in the kidneys to regulate how much water is retained/excreted in the urine. Potassium and others have roles in making yor mucsles contract. Calcium is obviously an important part of bone but it is also used when cells signal each other. Though in every person the concentrations are slightly different and change from moment to moment in each cell of the body, they are usually quite tightly regulated, and large disturbances can cause serious medical problems. You mention that your physician told you to include electrolytes in your diet, but did not mention which ones specifically, so it is hard to give good examples of what to eat, but in essence all food contains electrolytes, the body simply keeps what it needs and excretes what it doesn't. If you have an electrolyte imbalance and you're eating a normal diet, either your normal values are part of the small proportion of people outside the normal reference values, in which case there is no problem, or there is an underlying medical problem that should be investigated. Sodium and chloride ions form common salt, so if you are low on these, a pinch of salt on your chips should help with this. Bananas are well known sources of potassium, as are potatoes and in fact most fruits and vegetables, including many fruit drinks. Calcium is obviously high in dairy foods, however both calcium and phosphorus absorption requires vitamin D. This is mostly derived from exposure to sunlight, as vitamin D is naturally rare in foods. However, if you don't get much direct sunlight exposure, try eating oily fish, tuna, salmon, mackerel etc, fish oil tablets, and fortified foods such as bread and cereals. If still in doubt, buy some cod liver oil tablets. Magnesium is present in green vegetables, nuts and milk. So basically, if you eat a good and varied diets with all food groups included, then you shouldn't be lacking in any electrolytes unless there is an underlying problem somewhere. If you still are concerned, try buying some oral rehydration tablets from a chemists. These contain most electrolytes and are used in cases of severe dehydration when simply replacing water lost would cause the electrolytes in the body to be diluted. These replenish the electrolytes as well so that water can be replaced in bulk volumes. I would also advise going back and asking for a copy of the electrolyte levels yourself (I'm assuming you have had a blood test to measure them that proves they are low, or is your doctor going by other symptoms?), so that you know exactly which ones are low. That way you can modify your diet more specifically.