The state migration service said the posts were "provocative" because they allegedly made fun of the economic hardships being experienced by many Turks.
The service said the seven have been arrested and will be deported back to Syria.
The incident highlights rising anti-migrant sentiment in Turkey during a new wave of economic turbulence that has seen inflation spike and the value of the lira drop.
President Recep Tayyip Erdogan says Turkey is now home to five million refugees and migrants -- most of them from war-torn Syria.
The scandal over the bananas started when a video went viral earlier this week showing a man in Istanbul shouting at a young Syrian woman and accusing migrants of "having have an easier life than us".
"I can't eat bananas and you buy them by the kilogramme on the market," the man says as an angry crowd gathers around the woman.
Some Syrians in Turkey responded by launching a protest movement against discrimination in which they posted videos showing them eating bananas.
The altercation occurred two months after a mob of men attacked the shops of Syrian migrants in the capital Ankara.
That violence was sparked by a street fight in which a Syrian migrant allegedly stabbed a Turkish man to death.
