As for whether you are drunk, you need a traffic police investigation, not an insurance company.
If you don't have a switch drive, you can have them check it. Don't worry, this will definitely compensate (without switch drive)
If you change drivers, you won't lose money. If it is drunk driving, it will not be compensated according to national laws. If you change drivers, it is cheating insurance, which will be illegal. Please consider it.