Write it in a sentence: “There are three twos in the English language.” or write “There are three meanings of the word to in English” or “There are three ways to spell too in the English language.” or figure out a way to write it out.
There are three theres in the English language. Their pronunciation is similar, if not the same. They’re easy to differentiate when used in any particular context.
“There are three English words that sound like /tū/. Two of them are too and to. The third word is very common; in fact you have just encountered it. What is the third word?”
Simple. Pronounce them as they were originally pronounced.
“To*,” “two**,” and “too*” have become homophones over time.
Prounounced something like “toe”
** Pronounced the way it’s spelled, with the “w” pronounced and rhymes with “toe”
*** Prounounced the way we currently prounouce it (well, there is a difference due to the Great Vowel Shift, but close enough).