Eating / Food and sleep

Eating before sleep (about 1-2h before naps, and 2-3h before cores) can significantly worsen sleep quality (Vital%) because digestion leads to lack of SWS and, when especially close to the sleep, even REM. Light-sleep is also made lighter, sometimes even causing a napaware where none would normally occur.

Along with worsening sleep quality, it also tends to throw off the circadian because food is a circadian indicator, similar to blue light. Some individuals are only marginally affected by this and as such, can eat in DP, whereas for many it has an effect even stronger than blue light.

Water doesn't count as food, but juice and such does - it needs digestion. 30 minutes before a core, it might make sense to not drink water either, though this has not been verified as the effect is likely very small. Sparkling water can have slightly more of an effect, but is also fine in DP.