You can check the cheapest coins in the crypto marketcap applications, the sorting features will help you find the suitable altcoins for your need. By the way, Dogecoin is the cheapest altcoin I know.
Invest in cheapest coins is always not a good choice. Instead, I do consider it is one of worst options, because cheapest coins are mostly dead ones. Ultimate goal of investment is profit, so what do you get by investing in cheapest coins at 1 satoshi for example, than at the end, you won't be able to sell them even at 1 satoshis? You will lose all of your money by investing in cheapest coins, that have terrible quality, and liquidity.
Buying a Dogecoin 1 month ago and selling now is profitable trade for me. Cheap altcoins shouldn't be considered as a preferable investing, the price is not what investors look for. Value and price performance are the two main indicators for me in order to filter such project altcoins.