Maaser Sheini 2:10

If a person has some sons who are ritually unclean and others who are ritually clean, he should put down a sela (a denomination of money)  and say: “May the sanctity of what the clean sons drink be transferred onto this sela.” In this way, the clean sons and the unclean sons may drink from the same jar.

Maaser Sheini 3:1

One may not instruct his friend to transport produce to Jerusalem in exchange for a share of it. One may, however, tell his friend, “Bring them so that we can eat them and drink them in Jerusalem.” People may give second tithe to one another as a gift.