What kind of preparation is needed to get an admission in executive MTech in data science in IIT Hyderabad?

Honestly speaking, Executive M.Tech or MBA in part-time or short-duration courses in newer IITs or NITs has zero effect on your career prospects and is not worth the money and time invested. Instead, it's better to invest 2 years for a full-time M.Tech in top universities like IIT Madras, IIT Bombay, IIT Delhi, IIT Kanpur, IIT KGP BITS, etc. Utilizing more time to prepare for six top universities will help you reach better heights career-wise. However, keep working and prepare for GATE alongside your job. In the meantime, you can clear BITS-HD, and PGEE for IIITs easily if you prepare at the GATE level. Even with an experience of 4 years, you can invest 2 years for M.Tech in top IITs and secure a good IT job in tech giants like Google, Amazon, McKinsey, etc. 

It's better to consider other options and leave Executive MTech as the last option when all doors are closed.