Diammonium phosphate or DAP is probably the most common yeast nutrient it can be used alone, and can also be bought blended in different proportions with inactivated yeast. Together they add both organic and inorganic nitrogen to the must. Personally, when I use a yeast that prefers a nutrient supplement, I tend toward the blended stuff, and prefer a two-stage feeding schedule, with 1/2 the recommended amount after the lag phase, and then the second half about midway through. Adding too much DAP is possible, especially with late additions to the fermentation, resulting in not all of the DAP being consumed by the yeast. It results in a somewhat jolly-ranchery/candy flavor in the cider/wine. I've met some commercial cider producers who do this on purpose in their sweet ciders.
As of yet, I haven't seen any studies specific to nutrient selection for cider as opposed to grapes, but there is no real answer to this question due to the wild range of fermentation properties between batches. How & where the apples are grown, the yeast used, the temperature, pH, and brix all influence the selection of nutrient, if it is needed at all.