What this mean in Tagalog they should be honest?

Here are a few ways to say "They should be honest" in Tagalog, depending on the context and level of formality:

Formal:

* Dapat silang maging matapat. (This is the most literal and formal translation.)

* Nararapat lamang na maging tapat sila. (This emphasizes the moral obligation to be honest.)

Informal:

* Dapat lang na magsabi sila ng totoo. (This emphasizes the importance of telling the truth.)

* Magiging matapat sana sila. (This expresses a hope that they will be honest.)

* Sana maging tapat sila. (This is a more casual way to say the same thing.)

Note: You can also use the phrase "dapat silang magsabi ng totoo" which translates to "They should tell the truth."

The best translation for you will depend on the specific situation and who you are talking to.