The safest answer for a guppy is familiar water, moved as little as possible
A guppy can stay safely with a trusted fish-keeper who has a small cycled spare tank, or in its own tank at home while a named helper visits. Guppies are tiny, fast-breeding tropical fish that chill quickly and stress in fresh, uncycled water, so the container matters more than the address. A sealed transport bag, a bucket without a filter, or a neighbour's goldfish bowl all fail within hours to days, even though each looks like water to a non-fish person.
Option one: a prepared spare tank at a keeper's home
A small spare tank kept by a fellow aquarist, a relative who keeps fish, or a family member willing to run it is the strongest away-from-home option for guppies. Ideally that tank is already set up with a mature filter, a heater holding a steady tropical temperature, a lid, and water treated for chlorine. Your guppies travel there in bags floated to match temperature, then are released into that tank only, never tipped in with the bag water.
Option two: the guppies stay, and help comes to them
Staying in their own tank is often kinder for guppies than any move, provided a helper can genuinely reach the house. The guppies keep their filter bacteria, plants, temperature and hiding places, and nobody has to catch fast, slippery fish under time pressure. The helper's jobs are small and specific: a tiny pinch of food once a day, a check that the heater light and filter are running, the light timer left alone, and a battery-powered air pump switched on if the power is out. Agree this arrangement in advance and leave the helper a key, because a plan that depends on finding someone during the emergency is not a plan yet.
What to rule out, however kind the offer
Well-meaning offers to avoid for guppies include a child's desktop bowl, a community tank full of larger fish that will chase or eat them, and any newly filled tank with no mature filter. Guppies also should not be released into a pond, a stream or a neighbour's outdoor tub, where they can be eaten, chilled, or become an introduced species. A local aquatic shop may agree in advance to board small fish, but that relationship has to be asked about on a calm day, not assumed while you are packing a car.
The short-notice kit that makes either option work
Keep a guppy go-kit beside the tank so either plan starts fast: strong fish bags and bands, a small net, a battery air pump with fresh batteries, a bottle of water conditioner, a few days of their usual food in a sealed pot, and a note naming the spare-tank host and the visiting helper. If fry are present, say so, because a host tank with a strong filter intake or hungry tankmates can lose them overnight.
If you have minutes, not hours
When leaving cannot wait, prioritise warmth and oxygen over a perfect relocation: bag the guppies with tank water and plenty of air, insulate the bags in a padded box, keep them dark and level in the car, and go straight to the prepared host. If nobody can take them, fill nothing new and change nothing in the home tank; simply feed nothing extra, confirm the filter is running, set the battery pump ready beside it, and message the visiting helper with the exact address and key details. Either way, record which option you used and who holds the guppies in KinsLe's Care Pass, so the person stepping in has the routine in hand and you can direct questions to one place while you are away.