Sri Lanka's immediate problem is not lack of tea or rice, it's that they're out of money and can't pay for imports of essentials like fuel. In other words, a currency crisis.
They're not making enough money to pay for imports because they're not producing enough. If they were producing enough then they wouldn't need to borrow money to pay for imports, so the cost of borrowing wouldn't matter.
> Production of tea -- Sri Lanka's main cash crop -- fell by 18% in a year. Production of rice -- the main food crop -- fell by even more.
The problem isn't the currency.