A translation of "[something] tastes bad"

„Das Essen schmeckt schlecht“ is absolutely correct and probably the most common way a native speaker would express the thought.

Intransitive schmecken describes the taste of something; you can also say:

• Das Essen schmeckt scheußlich. – The food tastes awful.
• Das Steak schmeckt wie Gummi. – The steak tastes like rubber.
• Der Kuchen schmeckt wie selbstgemacht. – The cake tastes like it's homemade.

And then there is schmecken nach which means “taste of,” like so:

• Die Kekse schmecken nach Zimt. – The cookies taste of cinnamon.
• Das Steak schmeckt nach Gummi. – The steak tastes of rubber.
• Das Essen schmeckt nach nichts. – The food tastes of nothing, bland.
• Küsse, die schmecken nach See, nach Salz und Teer. – Kisses that taste of the sea, of salt and tar.

It is true that intransitive schmecken without any qualifier means “taste good” (or at least acceptable!). Therefore you have:

• Schmeckt's? – Does it taste good? (Infamous question presumably asked by annoying waiters, though in reality they tend to say Alles in Ordnung?)
• Das Essen schmeckt nicht. – The food does not taste good. (That is to say, it tastes bad.)

Bonus fact: Riechen (to smell) has the same duality of a transitive and intransitive use; plus, it can also be used with nach just like schmecken. Except that without any qualifiers, it does not mean “smell good,” quite on the contrary: Das Essen riecht is not a compliment.