If you are a student in the United States on an F-1, J-1 or other student visa, you may require a document to establish Curricular Practical Training (CPT).
Please talk to your school's international student affairs office for more details. Google can not provide you with any kind of CPT or OPT authorization.
Starting with Google Summer of Code 2019, all accepted participants will receive an email confirmation of acceptance into the program. The letter may or may not be sufficient for your purposes. We send the letters within a week of announcing which student projects have been accepted.
We do not offer customized letters.