The configuration is the following:
@ReportsCrashes(formKey = "",
formUri = "",
formUriBasicAuthLogin = "",
formUriBasicAuthPassword = "",
httpMethod = org.acra.sender.HttpSender.Method.PUT,
reportType = org.acra.sender.HttpSender.Type.JSON,
mode = ReportingInteractionMode.TOAST,
resToastText = R.string.crash_toast_text)
It works with POST.
Best regards.