The duo will replace Chris Gayle and Andre Russell, both of whom have left to play in the Bangladesh Premier League.
Hyatt is a right-hander who has played nine One-Day Internationals but who failed to make the 13-man squad for the first game against Windward Islands which Jamaica won inside three days on Sunday.
The 21-year-old Cotterell, meanwhile, has only played Twenty20 cricket to date, taking five wickets in three matches during the recent Caribbean T20 campaign.
Jamaica will miss both Gayle and Russell who were instrumental during Jamaica’s win last weekend.
Gayle smashed 165 in the second innings while Russell grabbed a four-wicket haul in the same innings to help rout the Windwards.