The expression "頬張る" means something like "mouth full", right?
So, how would you use it to say "Akane's mouth full"? I don't know how to conjugate it. 😕

Please write the polite and casual ways. 🙏

質問を翻訳

Your idea is coreect.

Polite
あかねは、リンゴを口いっぱいに含んでいる

Casual
あかねは、大きな口を開けて、リンゴを頬張っている

The differences between Polite and Casual is a little. But 頬張る is relatively writing word, so we usually don't use it in our daily conversation. Instead of that we often use “食べている”