It works for text files, but fails for xlsx. it gives no error, and file is corrupted. Not sure if the content type is correct
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls -bor [Net.SecurityProtocolType]::Tls11 -bor [Net.SecurityProtocolType]::Tls12
$filename = "Test.xlsx"
$api = "https://graph.microsoft.com/v1.0/sites/10b44bd9-97fa-4666-b735-6ac0868a04c1/drive/root:/General/"+$filename+":/createUploadSession"
$responseCreateUploadSession = Invoke-RestMethod $api -Method 'POST' -Headers $Headers
## "https://graph.microsoft.com/v1.0/sites/20b44bd9-97fa-4666-b735-6ac0868a04c1/drive/items/01CLOFTIEVJ25ZIZLHKVA3Q3HXB67OWT2G/createUploadSession"
$filePath = "C:\Users\Downloads\"+$filename
# Convert the file into ascii code and get the file size in bytes
$fileInBytes = [System.IO.File]::ReadAllBytes($filePath)
$fileInAscii = [System.Text.Encoding]::ASCII.GetString($fileInBytes)
$fileLength = $fileInAscii.Length
$accesstoken=$Headers.Values
$headersNew = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$headersNew.Add("Content-Length", $fileLength)
$headersNew.Add("Content-Range", "bytes 0-$($fileLength-1)/$($fileLength)")
$headersNew.Add("Authorization", $accesstoken)
$headersNew.Add("Content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
$body = $fileInAscii
$responseUpload = Invoke-RestMethod $responseCreateUploadSession.uploadUrl -Method 'PUT' -Headers $headersNew -Body $body