There are a number of casino's in the resort, quite a few attached to hotels. ( Hotel Kuban, Hotel Diamond in resort centre to name but 2) Biggest casino I believe is adjacent to Hotel Hrizantema about 500 yds from centre.
Don't think there is any major dress codes but it is easily checked by enquiring soon as you get there. I believe drink prices are similar to clubs in resort.

Toonman

Thanks for your help

Hi Rav, we normally frequent the casino at the Hotel Hrizantema. You have to take your passport for the first visit, to register. there is no charge for registration or entry. Smart dress code is required. There is a texas holdem (no limit) Poker tournament twice weekly, entry cost to the tournament is 110 Euro. Good luck

Update as just got back

Went to a couple of casinos and the entry was simple with details of name nationality and where you were staying in Sunny Beach.

As regards dress, depends on Casino and time of day, but generally no real code to follow, we went into Kuban Casino at around 4.30 one afternoon dressed in shorts, t shirt and trainers.

Also free drinks and food etc.

Machine stakes are really low less than 0.01 lev per spin and electric roulette starts at 0.30 lev (13p) per chip. Other gaming tables, roulette, blackjack etc start at 0.50 lev (22p) per chip.