Learn Dutch: Elke dag drink ik koffie. - Every day I drink coffee.

Because the sentence starts with the time phrase Elke dag. In Dutch, the main verb always takes the second position. When you put a time or frequency phrase at the beginning, the verb and subject have to swap places. This is called inversion: [1. Elke dag] [2. drink] [3. ik].

If I want to start the sentence with Ik, where does elke dag go?

If you start with the subject, the word order returns to normal and the sentence becomes Ik drink elke dag koffie. Time phrases and frequency words like elke dag, vaak, or altijd usually go right after the conjugated verb.

Why does it say Elke with an 'e' at the end, rather than just Elk?

Because dag is a de-word (de dag). Whenever you use the word for 'each' or 'every' with a de-word, you must use elke. If you were talking about a het-word, like het jaar (the year), you would drop the 'e' and say elk jaar (every year).

Can I replace elke dag with a single frequency word like vaak or soms in this exact word order?

Yes, absolutely! You can say Vaak drink ik koffie (Often, I drink coffee) or Soms drink ik koffie (Sometimes, I drink coffee). Putting the frequency word at the very beginning of the sentence just places extra emphasis on how often you do it, but you must remember to keep the verb and subject swapped.