Can minoxidil 2% solution be applied to a male in his early 20's with sparse hair ?

Should be able to. Be sure to read the directions fully and read any contraindications to be sure that male has none of those.

Minoxidil is FDA approved for male balding, also called androgenetic alopecia.

There are many reasons for sparse hair, and without seeing your scalp it is not possible to confirm you have androgenetic hair loss.

However, if this is confirmed you can indeed consider minoxidil provided you don't have any medical/health contraindications.

Men with genetic hair loss often consider the 5% strength as it has proven more effective than the 2% strength. Both. however, are FDA approved for the treatment of genetic hair loss.