Kiev?
Went there last year with a few friends and it was awesome, plenty of horrible trashy bars and plenty of cool local bars too.
Can visit Chernobyl if the budget allows (~£100pp) which i'll be doing again for sure!
A tip, set the date, set the destination and set the date you're going to book the hotel and flights. Tell people that unless they want to sort their own digs and transport then you need the money the day before the booking date, no exceptions.
Too many people half heartedly commit so you're left trying to work out how many beds to book and waiting on people dragging their heels, especially if it's a larger stag do. You also risk booking a bigger airbnb/more hotel rooms and risk being left to stump up the difference yourself or try and split it between those already going.
I took 18 people to Barcelona and somehow got them back alive and with no dropouts that way!