If you are a W-2 employee, then everything of value that you receive from working is part of your taxable income and should be reported on your W-2.
However, this does not include legitimate work related expenses that your company reimburses you for under an accountable plan. The company is also allowed to provide what is known as a “working condition fringe benefit“ that is tax free to you for expenses that would otherwise be deductible if you were able to deduct them as an employee. It’s not clear to me from your description whether the extra $50 would be considered taxable income, or a work condition fringe benefit, or an accountable reimbursement.
If you believe it should be taxable, then you can enter it in the other income or uncommon income section as miscellaneous income.
