Question

Fill in the blank with an appropriate word:there is a great demand___ Indian sweets

Answer 1

there is a great demand (of) indian sweets

Answer 2

There is a great demand for Indian sweets.  

  For is the preposition used to express a purpose, reason or use of a something or someone. The word 'demand' is usually followed by prepositions for, of, in, on, from, by, depending upon the meaning it conveys.  

  The word 'for' is widely used after the word 'demand' and represents the need for the resource. Hence in the above sentence, 'for' is used.

  For eg., the "demand for water" is more in summer.