Hi Salla. If you really do end up going for the 'sucking up a tube' option (oh dear!), then I'd be inclined to use a clear tube and when you can see the petrol is over halfway up the visible part (the bit that's not inside the tank), then aim the tube very quickly downwards into whatever receptacle you plan to collect the petrol in. The end of the tube will need to be lower than the petrol tank to maintain the flow. Hopefully, this should avoid a nasty gob-full of petrol. You'd still get a lung-full of the fumes mind you.
I have to say though, I wouldn't recommend it! I'd rather forego the petrol and not put myself at unnecessary risk.