I think that 200 bytes for heap is not enough.
I tested with heap = 200 bytes and got
Then I changed the heap = 0x200 and got
If your program is bigger then you may need more.
I used CY8CKIT-059
#define STR_BUF_LEN 32
char str[STR_BUF_LEN+1] ;
float f = 0.0 ;
CyGlobalIntEnable; /* Enable global interrupts. */
UART_PutString("UART Float Test\n\r") ;
sprintf(stringbuffer, "(%.1f, %.1f)", 1.1, 1.1);
snprintf(str, STR_BUF_LEN, "(%.1f, %.1f)\n\r", f, 1.1) ;
f += 0.1 ;
(Edited) Some typos fixed.
moto-san is correct about increasing the heap. You may also need to make sure the stack many need to be increased.
It appears you got the floating point library setting correct.