Budapest to Istanbul (train)
Budapest to Belgrade (€15) Mav-Start 8 hours
There is a wait in Belgrade for the connecting train of about 15 hours, if you’re not in a hurry it’s a great opportunity to explore Belgrade (often written as Beograd) the kalemegdan (fortress) is especially worth visiting.
Belgrade has a left luggage option which can be found just round the corner by the bus station.
Belgrade to Sofia (€20) Serbian Railways sleeper/couchette 10 hours
There is also a wait here for the connection this time of 11 hours and while this is also an opportunity to explore Sofia (often written as Sofya) it is not as beautiful or interesting as Belgrade. Papaya offers good value breakfasts which can be found on the main road Maria Luiza Boulevard (it connect the train station to the city centre).
There is also a left luggage option at the train station. Ignore anyone approaching you to offer you ‘information’ and showing you a badge, they are scammers.
Sofia to Istanbul (€20) BDZ sleeper/couchette 13 hours
Bursa to Budapest (bus)
Bursa to Sofia (€30) Metro Turizm 13 hours
Sofia to Budapest (€48) Eurolines/Kapat-C 12 hours