Rasna has gone international without significant market share in India. I really don't that its a great idea to go for market development when you don't have a stable market in your domestic.
Well, if we look at the competitors that took the market share away from Rasna are packaged juices and carbonated drinks. Kids no more want to buy Rasna, as it is tedious to prepare it and they may even not be satisfied with the taste. There can be other factors too.
Well, if we see through BCG matrix concept, the brand is a dog with low market share and low potential. As such, the only way is to diversify.
Rasna can enter into other categories like juices, etc and invest on all P's of marketing mix. It need to innovate the product, manage the distribution channel to enable accessibilty of the product, price competitively and promote. It may take up a different brand name altogether as Rasna as a brand doesn't have great equity to leverage it to the diversified product. Conversely, if the company uses Rasna as the brand name for diversified product, it may require less efforts to lead the brand to evoked set of customers as the brand is known to customers and recall is quite high.