Question: What should I use for havdala during the nine days?
Answer: While one may not drink wine during the nine days unless it is within a seudas mitzva, the Shulchan Aruch (OC 551:10) writes that one may drink wine for havdala as it is no different from a seudas mitzva (Mishna Berura 551:67). Thus, common Sephardic practise is to drink the wine (Kaf Hachaim OC 551:152).
The Rema disagrees, saying that we should give it to a child when possible. The Mishna Berura (551:70) explains that this child should have reached the age of chinuch though not be old enough to understand what we’re mourning about (6-9 years old).
The Aruch Hashulchan (OC 551:26) writes that one should rather use beer. It is debatable, however, whether beer is still considered to be chamar medinah nowadays. The Mishna Berura (272:24) writes that this only applies where beer is commonly drunk; R’ Moshe Sternbuch (Teshuvos Vehanhagos 4:77) writes that coffee and tea are more suitable. R’ Yehoshua Neuwirth (Shemiras Shabbos Kehilchasa 2:60:4) allows one to use cider or fruit juice if necessary, providing that they are considered important drinks in that locale.In conclusion, it would seem that those who make havdala on motzaei Pesach over beer should do so during the nine days. Otherwise they should make havdala on wine. If there is a child (preferably a boy between 6 and 9) available, they should be given the wine. Otherwise, one should just drink the wine oneself.