If you have no taxable income then there is really no reason to even file. But if you insist on filing then do not enter anything and print and mail the return. You cannot e-file a zero income tax return.
[Suggestions to enter $1.00 of fake income so that you can e-file will probably work but remember, you sign the return under penalty of perjury that the tax return is true, complete and accurate to the best of your knowledge and entering fake income is not filing an accurate and true tax return.]
If you are a student, over age 23, and are not claimed as a dependent by someone else (e.g. your parent) you may be eligible for the up to $1000 refundable American Opportunity (tuition) Credit. That credit is not dependent on having either kids or earned income. You must be at least a half time undergraduate student. There's even a loop hole available to claim the credit, if you are on scholarship.
Note that the $1 of interest gimmick is just to allow you to E-file. You can still file a paper return with $0 income in order to claim the stimulus payment.
To be eligible for the stimulus, you not only must not actually be claimed as a dependent by someone else, you must also not even qualify, under the dependent rules, as a anyone's dependent.