Sisto has impressed for Midtjylland, becoming one of the standout players in the Danish top-flight with his dribbling skills and pace.
The winger has contributed three goals in the league so far this season, and recently earned his first cap for the Denmark national team on the back of his fine form.
Although Sisto is only 20-years-old, he has already shown that he is ready for regular first-team football and is considered to be one of the most exciting talents in Europe.
Everton have created a young squad at Goodison Park, with the likes of Ross Barkley, Romelu Lukaku and Gerard Deulofeu all looking like exciting attacking prospects, and the addition of Sisto would add further depth to those ranks.
West Ham, meanwhile, have been keen to add pace and power to their attacking unit since Slaven Bilic took charge, and Sisto would certainly offer them those characteristics in abundance.
With City also tracking Sisto, their chances of landing the hot prospect could be limited, though, due to the financial strength of Manuel Pellegrini's side.