If you’re traveling in USA and TSA allows you to bring the little baggie of toiletries including liquids in your carry-on bag, you can put it in a mouthwash bottle and include it in the baggie as long as you don’t exceed the amount of allowed ounces. Note that if you’re going internationally, the baggie of toiletries might not be allowed, in which case anything liquid needs to go in a piece of checked luggage.
You can always put some holy water in a tightly sealed bottle- I recommend a screw top plastic bottled water bottle, like Dasani; don’t use any pretty holy water bottles, they may leak - and put it in your checked bag. Be sure not to fill it totally full due to pressure changes. If it leaks, you’ll just end up with your clothes getting a little Holy and wet. I have brought back Lourdes water and Sea of Galilee water in this way in my checked bag.
