It would taste like a low-alcohol or non-alcoholic beer. It had a sweet taste but an extremely low alcohol content, we are talking 0.5 to 3 %. Now we are talking 8th to 13th century. From the 14th century onward, more spices became available they were sometimes added to the more expensive beers to improve the taste.
In medieval England, ale was an alcoholic drink made from grain, water, and fermented with yeast. The difference between medieval ale and beer was that beer also used hops as an ingredient. Virtually everyone drank ale. For a beer, the wort had to be boiled with the hops.
It was the beverage of choice of urban populations that lacked access to secure sources of potable water; a commodity of economic as well as social importance; a safe drink for daily consumption that was less expensive than wine; and a major source of tax revenue for the state.