Any money that your employer pays you is just additional wages, the same as if they gave you a raise or a bonus. It should all be included in your W-2, and it's all taxable income. It doesn't matter why they say they are paying you the additional money. There's no such thing as a donation from an employer to an employee. Your employer can deduct all the wages that they pay you as a business expense.
You might be eligible to claim a federal tax deduction for interest that you pay on your student loan. The deduction is based on the amount of interest that you paid during the year, not the total amount that you paid. It's what's called an "above the line deduction," not an itemized deduction. You do not have to itemize deductions to claim it. Here are links to some information about the student loan interest deduction.
There are a few very limited cases in which your employer is allowed to pay off your student loans and not have it be considered taxable income to you. This generally applies to certain “public service“ or other jobs at nonprofit organizations, where you are offered a certain amount of loan forgiveness in return for a certain number of years of service. You would have to provide more details about your job and your situation before we could attempt to offer an opinion on whether you would qualify. This is a very complicated area of tax law, and it might be better to get professional advice.
In all other cases, the previous answer is absolutely correct.
1. IRC section 108(f) allows certain employers to make tax-free student loan payments for the student, called LRAP program (loan repayment assistance programs). It usually requires some form of public service, although this is different from "public service loan forgiveness" (where the government forgives the loan after you meet certain requirements). If your employer does not already have an LRAP, I doubt they can set one up on short notice, it's complicated and very technical, and professional help will be needed.
2. The CARES act seems to have temporarily included student loan payments in the $5250 annual limit for tax free education assistance. That means that if your employer already has a tuition assistance program, they can add student loan assistance to the program for 2020 only. Payments of up to $5250 total (for combined tuition and loan assistance) can be tax-free to the student.
However, if your employer does not already have a tuition assistance program, there are a number of challenges to setting one up. Key is that any qualifying fringe benefit program must be offered to all similarly qualified employees, it can't be just you. More information on fringe benefit programs is found in IRS publication 15-B.