Basing on the price only and call it the cheapest altcoin is not attractive, look for the undervalued coins, because that's the real cheap.
I'm saying coins because there's a lot of undervalued coins now and that is because of the bear period, I'm sure when the price starts to rise, people would say the popular words "I wish I bought when it's still cheap", let's learn from the past, be smart now and start buying the most undervalued coins.
It's wise to look for undervalued coins with good potential. Not all cryptocurrencies are worth the investment nowadays, since most of them are copies one from the other. You would need to explore a specific cryptocurrency you like, in order to determine if it's suitable for you. There are some cheap altcoins that are worth buying due to their active development and innovation. But others, are simply a loss of money because of their limitless supply and abandonment by their developers.
Of course, this current bear market has brought us a huge opportunity to grab many of the well-known altcoins at a discounted rate. If you're lucky, you'll be able to obtain some profit within the next bull market run, if the specific cryptocurrency you've bought, becomes highly viral.
Nonetheless, if you really want a good altcoin that's among the cheapest of them all, then I'd suggest that you consider Dogecoin.