Encourage your mom to drink bouillon and salty soups. Adding more salt to her diet by way of salty soups and snacks will help her better retain fluids.
Chocolate is the thing that give the most energy and quickly.
I hope this help.
You can have your mom drink coconut water also; it is very good for electrolytes and it's natural so it does'nt have the sugar like gatorade or powerade. You can get it at Wegman's in the Health Food section or at a Health Food Store; it comes in a container like a juice box. I have found the ZICO brand to taste the best.
I wish your Mom the best,