Can a child on ritalin (methylphenidate) drink an energy drink for extra help?

Yes, but why? If your child is already on a prescription medication where the dosage and actual medicine are well defined, why add a hodgepodge of substances that something like an "energy drink" is apt to contain? If the effect isn't quite right, speak with the prescribing doctor about what needs to change and see if you can adjust the medicine to make it work better.
Ritalin+energy drink. All energy drinks are laden with coffee, and no kids should ever be exposed to coffee (so, no brown soda as pepsi-coke-rootbeer- or even mountain dew which has the highest concentration of coffee while not appearing brown). Kids must learn healthy lifestyle when young: soda has 10 tea spoons of sugar per can + coffee = super active kids.

Related Questions

If you take ritalin (methylphenidate) and energy drinks what can happen, side effects?

A Lot. Dose of Ritalin (methylphenidate) if 5 mgm, and an oz of ED, I think you can wait out your entire life to say " Good gracious Lord, nothing happened .. "Why Lord ?" Now go on adding the doses 120 mgm of Ritalin (methylphenidate) and few gallons of ED, monstrous looking cans Lets see how long it takes for you to ask the Lord "Why Lord" It will be pretty quick response from the Lord. Read more...