Six glasses are placed on a table in a row. The first three are empty, and the last three are filled with water.
How can you make the empty and full glasses alternate, if you are allowed to touch only one of the glasses?
Rem:No pushing one glass by another.
Source: Russian "Kvantik"
Easy. (Actually, too easy).
Pour the 5th glass into the 2nd. Hopefully the 2nd glass is smaller than the 5th, in which case you can take a sip and still manage to have the 2nd glass full.