Biscuits that are low on sugar and fat and snacks that are not fried and not high on salt are okay. But the quantity should be taken care of. The snacks can be baked or roasted, with less salt, sugar and fat content.  Preferable snacks can be in the form khakhra, roasted diet chivda, fruits, a mixture of kurmura, groundnut and roasted chana, or sprouted pulses etc.