Tokyo agreed to deals with Burns and Sandaza following the departure of Yoshinori Muto, who joined Bundesliga club Mainz for 3.79 million dollars in May.
Burns, who was part of the Australian team that won the AFC Asian Cup in January, was the A-League's Player of the Year last season after scoring 13 goals in 24 games for the Wellington Phoenix.
"Officially signed for FC Tokyo," Burns said on his Twitter account. "Excited for my new challenge."
Sandaza meanwhile comes to Tokyo after spending one season with Spanish club Girona, where he scored 16 goals in 38 appearances.
Tokyo, who are currently second on the J-League standings, will kick off the second half of the season six points behind leaders Urawa Red Diamonds.