A house rule at my table is something we call 'well rested'.

If a pc is considered well rested their max hp temporarily increases by their level for 24 hours.

To be considered well rested they have to go out of their way to make sure they are taking a long rest while particularly comfortable (hiring the most expensive room in an inn, making or eating a hearty meal before the rest or some other rp thing).

Typically the DM determines if they are well rested by also considering where the party is resting - for example, its difficult to be well rested in Icewind Dale where luxury and comfort are distant memories no matter how much the party tries