re: Using Square to pay off non-CC accepting debts, earning rewards, etc.

the ink cash gives $200 rewards when $3000 is spent within the first 3 months. it also pays 1% of any purchases. and has 0% for 6 months

my student loan's interest rate is 3.75%


so, if I use square to put 3k or so on my ink card, then put that amount to my student loans... as long as i pay the ink off in 6 months, is there a downside?