What are the avenues where startups can invest excess funds?

Practically, I have seen Startups investing in liquid Funds I.e Debt oriented mutual funds as the funds raised are not immediately required for business use. The restrictions are too long that it is difficult to think of any avenue. You could take an opinion that short term highly liquid mutual funds are more of cash equivalents and not securities. Alternatively, in case there is a scrutiny in the year of fund raised and officer asks whether form 2 is filed with DPIIT, you could say no we do not fulfill the criteria. and you would then have to prove the identity, genuineness and credit worthiness of all investors viz covering letter, ITR copy and extract of bank passbook/statement.