can a 15ml cleanser last for 3 weeks??

you'd really have to ration it per cleansing. and at the rate, may not be effective. I think 3 weeks would be tough.

Oof 15 ml for 3 weeks. even if you use half a teaspoon of cleanser which is like 2.5 ml. This would last you almost a week. I say 50ml is about right. The Sephora at my country has travelling size producgs near the cashier. I would get a fresh bottle of sunscreen at the place you are visiting if possible Cleanser is pretty durable enough to be transferred to another container for 3 weeks. Sunscreen, not so much. Many Asian sunscreen tend to come in a 50ml bottle. Not sure if that is enough for the whole body. Maybe just the face.

I don’t think so. I was in a similar position and the cleanser lasted me about a week and 2 or 3 days

hmmmm no. if you will use in the am and pm routine. it will not be enough.

I don't think it will last for 3 weeks... even without sunscreen, you still need much amount to clean your face from polution etc so maybe have bigger cleanser to bring with you to avoid pimples etc.