わたしは'ケーキがいちばん すきです. --> わたしはケーキがいちばんすきです。
My favourite is cake. --> In literal Japanese translation would be "I like cake the most".
おさがすきのむ. --> おちゃ or こうちゃをのむのがすきです。(English tea = こうちゃ)
I like to drink tea.
food = たべもの
drink = のみもの
like to eat = たべることがすきです (*want to eat / would like to eat = たべたいです)
like to drink = のむことがすきです(*want to drink / would like to drink = のみたいです)
*We don't use apostrophe, nor put space between the words, and use the Japanese period (。).
Good job! Please enjoy learning. I hope this was helpful.