- 1 gallon per person per day for drinking and sanitation (per ready.gov)
- Water filter in case you need to drink from a stream
As for a water filter, many available nowadays are very effective, easy to use and compact. The one that came highly recommended from one of our super-outdoorsy sons is the Sawyer Mini, which "Removes 99.99999% of all bacteria, such as salmonella, cholera, and E.coli; removes 99.9999% of all protozoa, such as giardia and cryptosporidium" according to the manufacturer. At under $20, how can you afford NOT to get one for your car camping adventures?
NOTE: Amazon links are affiliate.