Sodium bicarbonate for the drains, best multipurpose stuff on the market, but a few little tubs of draino or some other brand can't hurt to have on the shelf ;)

Tyre repair kits are cheap as chips, have 4 packets and in addition to that about 8 sets of spare tyres and rims. (5 of those sets are brand new).

Mate, the lists are "never ending" and so much more is always needed, main thing is, to have the basics covered, the rest is all a case of "improvize, overcome and adapt" with what you have.

Was literally the case when we got flooded last month and stuck there.

Moved in, got flooded that night and cut off from everyone and everything. No electricity, no flowing water, but we made it all work with what we had. Some food preps, our BOBs and our cars (for charging the phones/comms).

All worked out well, all things considered.