Learn Russian: Дети едят булочки с чаем. - The children are eating buns with tea.

Есть (to eat) is one of the few highly irregular verbs in Russian. In the third-person plural (they eat), the correct form is едят. As a reminder, the full present tense pattern is: ем, ешь, ест, едим, едите, едят.

Wait, shouldn't the accusative plural of булочка be булочек?

No, because булочка (bun) is an inanimate object. In Russian, the accusative plural for inanimate nouns is exactly the same as the nominative plural (булочки). The form булочек is the genitive plural, which you would only use for the accusative if the noun were animate (like people or animals).

What case is чаем in, and why?

It is in the instrumental case, triggered by the preposition с (with) to show accompaniment. The nominative form is чай; since it ends in -й, the instrumental ending is -ем (чаем).

Is it more common to say drink tea with buns (пьют чай с булочками) or eat buns with tea (едят булочки с чаем)?