The flight is at 6:40 am, have to be there by 4 am.
Assuming there is no public transport at this hour, do the hotels offer transport to the airport?
Unless you’re staying in a very upscale hotel, free airport transport is very unlikely as it’s almost an hour‘s drive away.
You can of course ask your hotel to book you a taxi or private transphare, but it won’t be cheap, would say upwards of €100 at least.
You might be better off staying in an airport hotel the night before.