The first problem is that Lisbon, like most cities on the Iberian Peninsula are a long way from each other.
Trains and Bus from Lisbon to Madrid takes at least 11 hours each way. Bus to Lisbon - Seville is slightly less. (No train)
If you only have one free day I would suggest that you would be better of visiting Porto, the second city of Portugal.
The train between the two takes 2hrs 45 mins and you can easily do a nice day trip without much stress.
If you were intent on Spain I would recommend Seville as it is smaller and more do-able in one day. Bear in Mind thoug it is very very hot in June, July, August. (+-40ºC daytime)
There is a night bus service from Lisbon Gare Oriente Bus Station as follows
Dept:: Lisbon Gare Oriente: 21:00
Arrive: Seville 5:45 (local time)
The return service is as follows:
Dept:: Seville 23;59
Arrive: Lisbon Gare Oriente: 06:00
Service operator is www.alsa.es
