All income must be reported unless there is a specific exclusion in the tax code.
Your income should be reported regardless of whether you receive a 1099. You will report this on Schedule C. Additionally, you will be able to take eligible expenses as deductions on this schedule as well.
Even if you don't have any expenses, this $100 will not generate any significant tax liability.
See the attached instructions for this schedule:
https://www.irs.gov/pub/irs-pdf/i1040sc.pdf
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
