You should use either pure (preferably distilled) water or alcohol. I've dosed my water bottle before, but the downside is that once you are tripping you no longer have any more water. Haha. Honestly, your best bet is to hide the hits somewhere on your person or to dose before you go inside. Blotters are fairly easy to hide just because they are so small, and if you have liquid just drop it on candies or mints or something like that.