This app was mentioned in 1 comment, with an average of 2.00 upvotes
Interсity+ trains go for 5:30 time. You can buy tickets (Kyiv - Dnipropetrovsk Holovny) at http://booking.uz.gov.ua/en/ (you'll have to print tickets though) or with this app for Android: https://play.google.com/store/apps/details?id=com.uz.bookinguz&hl=en (it's official app, you don't need to print tickets, just show QR code on screen).